There are lots of food rules in the Torah. Rules forbidding **** and rabbit, rules forbidding eating creepy-crawly things, rules forbidding eating shellfish, rules forbidding mixing milk and meat. Those rules apply at all times and places (although you can violate any of the food rules if the alternative is starvation). Passover has its own additional rules, all centered on prohibiting leavened grain products. These rules apply to wheat, rye, oats, barley and spelt, and forbid even the remote possibility that these grains or products derived from them have come into contact with water for long enough to allow fermentation to begin. The one food that may be prepared from these grains is matzah, unleavened bread, where the time from mixing flour with water to the completion of the baking pro