Preheat oven to 350°.
Butter/oil a tube/angel food cake pan and set aside.
In an electric mixer, cream sugar with 1/2 C butter.
Add 2 C flour + the next 5 ingredients (through the vanilla).
Beat on low speed until blended, then on higher speed for 3 minutes.
Stir in 1/2 C chocolate chips. (This is half of the chocolate chips.)
Spread 1/2 of batter into prepared pan.
Combine remaining 1/2 C of flour, brown sugar, and cocoa in a medium bowl
Cut in remaining 1/4 C butter with a pastry blender until the mixture resembles crumbs.
Add remaining 1/2 C chocolate chips and nuts (optional).
Pour half of the the topping mixture over the batter in the pan and then repeat the layers with the remaining batter and topping.
Bake for 50-60 minutes.