Severity of meat and milk: Meat and milk combined is more severe than other forbidden foods. One who consumes other forbidden foods in an abnormal fashion has not transgressed a Torah prohibition, but one who eats meat and milk even in an abnormal fashion (e.g., they’re boiling hot, or mixed with a bitter substance) breaks a Torah prohibition.
Eating meat after milk: Laws of meat and milk on this day are no different than any other day. There is no lenience because of the holiday of Shavuot. Therefore, someone who wishes to dine on meat after eating dairy must observe five directives: [A] the dairy food must be eaten first, [B] one must clean the table or switch the tablecloth, [C] wash out one’s mouth and eat some bread or a fruit (it must be fruit that needs chewing, and not a fruit that sticks to one’s gums), [D] clean one’s hands, [E] bless Birkat Hamazon or the appropriate after-blessing after the dairy food.
Yellow cheese that is soft, and similarly cottage cheese, are not considered “hard” cheeses (see next paragraph). Nevertheless, some people wait an hour after eating them before eating meat.
If one ate hard cheese, which aged outside more than six months, one must wait six hours before eating meat. If it aged less than six months, then one should wait an hour per month.
Rinsing one’s mouth may be done by brushing one’s teeth. However, one must be careful on Yom Tov [A] that one’s gums do not bleed when brushing and [B] to use a liquid tooth cleanser. If there is a chance of bleeding, or one doesn’t have a liquid cleanser, then one should eat bread and rinse out one’s mouth before eating meat.
In difficult circumstances, it is sufficient to examine one’s hands (to be sure that there is no dairy food or grease on them) without washing.
Milk after meat: One who ate meat or a food containing meat and wishes to have milk must [A] wait six full hours after finishing the meat before he starts having milk, [B] switch the tablecloth, [C] say Birkat Hamazon or the appropriate after-blessing. .
Beef or poultry soup has the same rules as meat, and likewise requires six full hours before eating dairy.
Food caught between the teeth: If one finds a piece of meat between one’s teeth, it should be removed, and there is no need to wait six hours after finding it. However, one needs to rinse one’s mouth before drinking milk.
Dairy or meat pastry: It is permissible to bake dough with cheese or meat if it is baked in a fashion that the cheese or meat is clearly visible. If it is not clearly visible, then the pasty must be made in an unusual shape, or only a small amount.
It is prohibited to bake bread with milk, butter, or animal fat, both on this day and all year round, lest one eat it by mistake with meat or milk. If one did bake such bread, one may not eat it, and even to eat it alone without any other food is forbidden. One may neither use its crumbs, nor make it in an unusual shape .
One who bakes dairy bread or cake in a hotel or for financial reasons must make the cheese in it clearly visible, or bake it in a way that makes it clearly dairy.
Baking in a meaty oven: When baking dairy food, bread or cakes in a permissible manner, as described above, one may not bake them in an oven in the same compartment where meat was roasted, grilled, cooked or baked unless that compartment is previously koshered. Koshering modern ovens for this purpose requires fulfilling four conditions: [A] One wait twenty-four hours after baking etc. meat, [B] clean the oven with a damp cloth, [C] one must use a different cooking tray/rack, [D] one must heat the oven to its highest heat, and it must burn at its highest heat at least one full minute. If one baked dairy food in a meaty oven without fulfilling all of these conditions, a rabbi must be consulted.
An oven with two compartments, even if it has rabbinical approval, should be checked whether one compartment heats up to yad soledet bo (42°C, 107.6°F) when the adjacent compartment is heated. If it does reach that temperature, then it is all considered one compartment. If it doesn’t, then they are considered separate compartments.
Someone who wishes to bake in an oven that was used by somebody who does not observe kashrut (the dietary laws) properly must seek rabbinical guidance as how to do so. Merely switching the racks and trays is not sufficient.
It is permissible to bake pareve food in an oven compartment in which dairy or meat was baked, and the pareve food may be eaten together with dairy food or together with meat, as long as the oven was clean. Some have the custom to wait twenty-four hours after baking meat or dairy before baking pareve. According to all opinions, one is obligated to clean the oven and trays of crumbs and residue from the dairy or meat food.
If pareve food was baked together with dairy food, or remnants of the dairy food were present in the oven when the pareve food was baked, one may not eat the pareve food together with meat, and it is considered dairy, and not pareve.
Eating on one table: When two people are sitting at the same table, one may not eat dairy when the other is eating meat, unless they are totally unacquainted. If they are acquainted, they may eat at the same table solely under the condition that they place on the table an object between them, and it must be an object that is not regularly placed on the table, in order to remind them to not partake from the other’s food.
Separation between meat and milk: Bread that was eaten from at a meat meal may not be eaten later with a dairy meal, since sometimes some of the meat is left on the bread, and the opposite is also true. If one regularly takes some slices of bread out of their wrapping before eating a meat meal, and leaves the rest of the loaf in the wrapping, then only those slices may not be eaten with dairy, and vice versa. If, however, one is accustomed to take slices from the bread still in its wrapping in the middle of the meal, then the whole loaf may be eaten with that kind of a meal only, be it dairy or meat.
The same is true of the salt tray in which one dips bread, or from which people take salt with their fingers to salt their food, since sometimes their fingers have the dairy or meat food on them. Someone who is stringent and uses separate salt-shakers (even though they are closed, and the fingers don’t touch the salt itself) will be blessed.
One should take care not to place meat pots over dairy pots or vice versa in the refrigerator or any other place, unless they are covered. Some people are stringent and place them one over the other only on a shelf without holes, but not on a rack.
Cheese with worms: It is forbidden to eat wormy cheese.
Fish and milk: The Sepharadim have the custom not to eat fish with milk. Those who follow the R”ma allow it..
Dairy and meat knives: It is not proper to cut bread with a meat knife, even if it is clean, in order to eat the bread with dairy food. The opposite is also true.
If one cut an onion or other sharp food with a meat knife one may not eat it together with dairy, and vice versa, without consulting a rabbi. This is true even if the knife hasn’t been used with meat (or dairy) for the past twenty-four hours.
Mixtures: If milk became mixed with meat (or vice versa), and the meat is sixty times the quantity of the milk, in most cases the food is permitted, but a rabbi must be consulted. Nowadays we do not rely on a gentile to taste the food for us, to detect whether he tastes milk in the meat or not, even if the gentile is unaware of its importance. If there is a taste of milk in the mixture despite the fact that the meat is sixty times the milk, it is obviously forbidden to eat it.
Covering a boiling pot is tantamount to shaking it. This comes into play if a drop of milk fell on a piece of meat in a boiling pot; if he covered it immediately, then the drop mixes with the entire contents of the pot, and if there are sixty times the drop then the contents may be eaten. If there aren’t sixty times the drop, then all of the contents are forbidden. (To nullify the drop is permissible in the case described only, but to purposely pour some milk into a meat pot, even if there are sixty times the milk present, is forbidden.)
The steam that rises from cooking food is considered as the food itself. Therefore, one who is cooking meat should not pass dairy food or pots over the steam from the meat. If he did so with a dairy pot, and the pot heated up to 42°C (107.6°F), the pot becomes forbidden. If he did so with dairy food, then even if the food didn’t heat up it becomes forbidden, since in any case the dairy food mixed with meat. Some say that even the meat being cooked becomes forbidden.
If steam from a range or oven is emptied by a vent, and the steam is still 42°C (107.6°F) when it reaches the vent, one should be careful not to heat meat and milk alternately under it. In such a case, if possible, one may heat the meat, and then cover the vent with tinfoil or the like before heating the dairy (or vice versa).
Similarly, one should not place an uncovered meat pot on one burner on a range and an uncovered dairy pot on another burner on the same range, lest their steam mix. (This is true even if the steam doesn’t reach the heat of 42°C.)
A microwave oven: Its rules are more stringent than regular ovens. If one wishes to cook in it meat and then dairy, or vice versa, one must fulfill the following directives: [A] use separate plates for dairy and meat, [B] wait twenty four hours between cooking one and the other, [C] clean the oven with a damp cloth and remove all remnants of the previous food, [D] insert a plastic cup with water, and turn on the oven until some of the water evaporates, [E] wrap and seal the food.