Place a rack in the center of the oven and preheat the oven to 350 degrees F. Place the ramekins on a baking sheet for easier handling, and set it aside.

Place the flour, sugar, 1 tablespoon plus 1 teaspoon of the cocoa powder, the baking powder, and salt in a medium-sized bowl and whisk to blend.

Place the beaten egg, butter, milk, and vanilla in another medium-sized bowl, and whisk to blend.

Pour the flour mixture over the egg mixture, and stir with a wooden spoon just until the batter is combined.

Stir in the walnuts and chocolate chips.

Spoon the batter into the ramekins, dividing it evenly between them.

Place the remaining 1 tablespoon plus 1 teaspoon cocoa powder, the brown sugar, and the boiling water in a small bowl, and whisk to mix well.

Pour the mixture over the batter in the ramekins.

Bake the cakes until a toothpick inserted in the center of one comes out with a few crumbs clinging to it, about 20 minutes.

Remove the baking sheet from the oven, transfer the ramekins to a wire rack, and let them cool for 10 minutes.

Serve the cakes warm, in the ramekins, topped with scoops of ice cream if desired.