If you like your brownies gooey, fudge-like, and slightly underbaked, you’ve come to the right place. Instead of creaming the butter with an electric mixer, which whips air into it, you’ll melt the butter with the chocolate to create a rich, thick base. Adding a yolk in addition to the whole eggs emphasizes the fudge-like texture. Though we often ask you to insert a toothpick into a baked good to test for doneness, that’s not the best method for this recipe, since you want the insides to be gooey. Instead, gently shake the pan. If the center jiggles, continue baking. If it’s firm and set, pull the pan out and let the brownies cool completely.