This gooey-centered chocolate cake, a popular sweet in Sweden, is called kladdkaka, which translates as “sticky cake.” With only six ingredients (not counting the salt) and an easy dump-and-stir mixing method, what’s not to love? For our version, we brown the butter to add a subtle nuttiness, and we use brown sugar for its molasses notes. The cake can be served warm or at room temperature. Top slices with whipped cream, ice cream or gelato.