1) Preheat the oven to 350°F. Grease four 1-cup ramekins or oven-safe mugs.
2) To make the cake: Mix together the flour, sugar, cocoa, nut flour, salt, and baking powder.
3) Whisk in the vanilla, melted butter or oil, egg, and milk.
4) Divide the batter between the prepared ramekins or mugs, using about 1/3 cup batter in each.
5) To make the topping: Whisk together the sugar, cocoa, and salt.
6) Divide among the ramekins or mugs, using two heaping tablespoons for each.
7) Top each ramekin or mug with 1/4 cup boiling water. Place on a baking sheet.
8) Bake the cakes for 18 to 22 minutes. The cake should be puffy, with some liquid boiling up around the edges.
9) Serve hot or warm. Top with whipped cream, a toasted marshmallow, ice cream, or a splash of Irish Cream, if desired.
Yield: 4 servings.