Preheat oven to 350 degrees F (177 degrees C) and place rack in center of oven. Place the nuts on a baking sheet and bake for 8-10 minutes or until fragrant and lightly browned. Let cool and then coarsely chop. Set aside.

Coffee Cake Topping: In a small bowl stir together the sugar, chopped nuts, chocolate chips, ground cinnamon and flour. Set aside.

Butter and flour (or spray with a non stick vegetable/flour spray) a 9-inch (23 cm) spring form pan. Line the bottom of the pan with a circle of parchment paper.

In a separate bowl whisk together the flour, baking powder, baking soda, and salt. Set aside.

In the bowl of your electric mixer (or with a hand mixer), beat the butter until softened (about 1 minute). Gradually add the sugar and continue to beat until light and fluffy (about 3-4 minutes). Add the eggs, one at a time, beating well after each addition. Beat in the vanilla extract. With the mixer on low, add the flour mixture (in three additions) and sour cream (in two additions) alternately, starting and ending with the flour. Mix only until combined.

Spoon half of the batter into the prepared pan, smoothing the top with an offset spatula. Sprinkle about half of the nut topping on top of the batter. Cover with the remaining batter and then sprinkle with the remaining nut topping. Bake for about 40 - 50 minutes, or until a toothpick inserted into the middle of the cake comes out clean. Remove from the oven and let rest for about 10 minutes before releasing the sides of the pan.

Serve warm or at room temperature.

Makes one - 9 inch (23 cm) cake.