While some brownies are too soft and cake-like, and other are too wet or dense, the best brownies fall somewhere in the middle of the spectrum. All, however, should have a deep chocolate flavor without being too sweet or one-note. Because baking is more of a science than an art, with kitchen chemistry as its foundation, you can bake brownies that are sure to come out right.

When you add wet and dry ingredients together in flour, stirring as you go, the proteins in the flour form gluten, a protein-like substance that holds in gas bubbles to help breads and desserts rise. But too much gluten, formed by high-protein flour or by working the flour too much, can also make baked goods tough. Because different flours contain different amounts of protein, you'll have more tender brownies if instead of all-purpose flour you use cake flour, which has a lower protein content.

When butter and sugar are creamed, they hold more gas bubbles that arise from baking powder or baking soda. Once the bubbles burst from the oven's heat, the brownie rises. Oil and melted butter don't hold bubbles in the same way as creamed butter, leading to a denser crumb. If you like brownies with a cake-like texture, cream the sugar with slightly chilled butter. For chewy, fudge-like brownies, melt the butter first or use a combination of butter and oil.

Ounce for ounce, unsweetened chocolate and cocoa powder contain more chocolate liquor, from ground chocolate seeds and nibs, than bittersweet and semisweet chocolate, which contain more sugar. Intensify the flavor of cocoa powder even more by pouring hot water over it to free the flavor molecules that are trapped inside protein molecules. You can also add some instant espresso powder to deepen the chocolate flavor.

The shiny and crackling crust that forms on the top of a brownie gives it both visual and textual interest. To ensure that your brownies have that feature, use only granulated sugar, which forms a crust when the sugar molecules rise to the surface and dry out. Brown sugar and corn syrup, on the other hand, contain more moisture than granulated sugar, so the surface of the brownies never dries out.