In a medium bowl, stir together 3/4 cup sugar, self-rising flour, 3 tablespoons cocoa powder, pecans and salt.
Add milk and vanilla, stirring until smooth.
Pour melted butter into an ungreased 1 1/2-quart baking dish.
Pour batter evenly over melted butter
In a small bowl stir together remaining 1/2 cup white sugar, 1/4 cup brown sugar, and 1/4 cup unsweetened cocoa powder. Sprinkle evenly on top of batter.
Pour hot water evenly over top.
Bake for 35 to 40 minutes. Let stand 5 minutes before serving.