You can make the batter for these ultrarich cakes, scrape it into the muffin tin, cover, and refrigerate overnight before baking. Please read About Flourless Chocolate Cakes.

Have all ingredients at room temperature, about 70°F. Preheat the oven to 400°F. Butter 9 cups of a standard muffin tin. Sprinkle inside the muffin cups:

Shake the sugar around the inside of the muffin cups to coat, then dump out any excess sugar.

Heat in the top of a double boiler or a heatproof bowl set over barely simmering water:

Remove from the heat. Sift into the chocolate-butter mixture:

Stir until smooth. Stir in:

Beat in a medium bowl on medium speed until soft peaks form:

Gradually add, beating on high speed until the peaks are stiff but not dry:

Use a silicone spatula to fold one-quarter of the egg whites into the chocolate mixture, then fold in the remaining whites. Fill the muffin cups about three-quarters full. Bake until the cakes look set on top but are still gooey in the center, 5 to 6 minutes (a minute or so longer if the batter has been refrigerated). Let sit for 2 to 3 minutes; the cakes will shrink slightly from the sides of the tin. Place a rack over the cakes and invert to unmold. Serve hot, accompanied with: