1) It must be made from the milk of a kosher animal. Butter made from camel milk, for example, is not kosher. (This is not usually a problem in the United States.) The only exception is mother's milk for a baby--but they don't generally make that into butter.
2) The equipment used to prepare it must be:
A) Kept from contact with anything non-kosher; and
B) Kept from contact with meat.
3) No non-kosher food or meat should contaminate the milk. (One would hope this were generally true for all butter!)
4) In order to guarantee that 1, 2 and 3 are followed, someone knowledgeable in the rules of kosher food must supervise the process. This is usually, but not always a rabbi.
There is nothing non-kosher in the ingredients for peanut butter and there are several brands of peanut butter that are certified kosher.
Yes, it is halal. They use microbial enzymes to make their cheese. Also, their butter is kosher and therefore their cheese is kosher too.
yes
Yes.
What?
Every butter, and almost all other purchased foods and drinks.
No.
As most brands of mustard contain vinegar, it does have to be certified kosher as many vinegars are derived from grapes. Additional factors that could render mustard unkosher would be its preparation with utensils or on machines that are also used to process other [unkosher] products, or in a large industrial setting where unkosher products are processed nearby, and the steps taken to maintain separation between the production lines are inadequate to guarantee that the separation is never breached.
Make sure all of the ingredients are kosher and the utensils and kitchen it's being prepared in are also kosher.
No, but there are kosher companies that make spices. Just look for the kosher symbols on the products.
Skim milk, whole milk, half-and-half, whipping-cream and butter are all potentially kosher for Passover. The only difference between these is in the butterfat content (none in skim milk, almost 100 percent for solid butter).
If the kosher caterer in question makes wedding cakes, the cakes in question would be kosher.