If I want to make something that involves cooking butter and brown sugar in a pot until it's a thick syrup, pouring it over matzah and have it set which it does quickly as it cools, and then put it in oven for a few min during which it hardens, is the butter/sugar considered a liquid when it goes in oven? Or more specifically, would I be allowed to make it open in a clean fleishig oven? The hardened butter/syrup would be quite thick when it goes into the oven, but may melt and liquify at some point while in there.