In a bowl, combine 1/2 cup of granulated sugar, the cinnamon, cocoa, and chopped nuts; set aside.
In a mixing bowl with an electric mixer, beat the butter with 1 1/3 cups of granulated sugar until light. Add the eggs, one at a time, beating after each addition.
In another bowl, combine the flour, baking powder, and soda; mix to combine thoroughly.
In a small bowl, combine the sour cream and milk or cream.
Slowly beat in flour mixture, one-third at a time, alternating with the sour cream mixture, one-half at a time, ending with the last flour addition.
Beat the mixture until smooth. Spoon half of the batter into the prepared pan. Sprinkle the filling mixture over the batter. Spoon remaining batter evenly over the filling. Carefully spread to cover.
Bake for 55 to 60 minutes, or until a wooden pick or cake tester inserted in center comes out clean. Cool on a rack in the pan for 10 minutes. Remove the sides of the pan and cool completely on rack.