When garlic cloves are chopped, the sulfur compounds and an enzyme called allinase, usually held separate within the clove, come into contact with one another. The collision generates the compound allicin, which gives garlic its pungency, and pyruvic acid, which is responsible for its spicy heat. But left intact, so that its volatile compounds don’t interact, garlic offers an entirely different character; roasting the cloves whole draws out their sweetness, yielding the sumptuous confit that adorns this pretty focaccia. Cook the focaccia on a pizza stone, which will give the bottom crust a delicious crunch.