Chocolate Cobbler

Chocolate Cobbler
Ingredients:
1 cup flour
2 teaspoons baking powder
1/2 teaspoon salt
2/3 cup sugar
1 1/2 tablespoons cocoa powder
2 tablespoons butter, melted
1/2 cup milk
1 teaspoon vanilla extract
1/2 cup chopped walnuts (optional)
Topping:
1/4 cup sugar
1/2 cup brown sugar
1/4 teaspoon salt
1 tablespoon cocoa powder
1 cup boiling water