If you take a bulb of garlic and bake it in the oven, the regular garlic flavor disappears and a very mild and sweet flavor takes its place. (Okay, admittedly, there is still a slight hint of garlic flavor.) This "heat kills the flavor of garlic" principle carries over into other things that I cook. I find that anytime I subject garlic to heat for about five minutes or more (like in a frying pan with oil), I start losing the flavor of the garlic. A typical example of this is when I add, perhaps, ten cloves of garlic to chili. There is hardly any garlic flavor left after I simmer the chili an hour or more.
Another example is if I add beans or, strangely enough, bean sprouts, to a dish, the flavors become muted, despite the fact that just after adding them, they were quite strong. This is particularly true garlic and herbs and ginger. (I have taken to just omitting bean sprouts from my Chinese recipes.)
Can you think of other examples of this principle in action? If so, how do you deal with it to retain or put back the flavors you want in the dish?