Chocolate lava cakes gained popularity in the late 1990s thanks to the chef Jean-Georges Vongerichten, and they have stuck around on dessert menus for good reason: They are rich chocolate cake and velvety sauce all in one, and they are surprisingly easy to make in under an hour. If you like to plan ahead, you can prepare the batter a day in advance, refrigerate it, then pop the cake into the oven when you are ready for dessert. This recipe, made in a 10-ounce baking dish, is meant for sharing, but you can also make it in two 6-ounce ramekins. Just cut the baking time to 7 to 9 minutes. Also, be sure to use chopped chocolate bars or chocolate fèves rather than chocolate chips here. Chips are made with stabilizers that inhibit melting and will negatively affect the texture of your dessert.