Recipe(tried): Tried and True Sour Cream Coffeecake

I have been making this coffeecake since the 1970's. It never disappoints me.

TRIED AND TRUE SOUR CREAM COFFEECAKE

FOR THE CAKE BATTER:
3 cups flour
3 teaspoons baking powder (or 1 tablespoon)
1 cup butter, at room temperature
1 cup white sugar
3 eggs, at room temperature
1/2 pint regular sour cream (not lowfat)
1/2 teaspoon baking soda (will mix with the sour cream)
1 teaspoons vanilla

FOR THE FILLING:
1/2 cup white sugar
1 teaspoon cinnamon
1/2 cup chopped walnuts
1/2 cup semi-sweet chocolate chips
-- Combine filling ingredients

FOR THE STREUSEL TOPPING:
1/2 cups chopped walnuts
1/2 cup brown sugar
1/2 cup flour
1/2 teaspoon cinnamon
1/4 cup butter
-- Combine streusel ingredients

1 well-greased Bundt pan

TO PREPARE THE CAKE BATTER:
Combine dry ingredients, except baking soda; set aside.

Beat eggs and butter, add sugar and blend until fluffy. Stir baking soda into sour cream, add vanilla. Mix the two mixtures until well blended.

TO ASSEMBLE AND BAKE:
Put half of the batter in pan, sprinkle the filling on top. Add remaining batter. Sprinkle topping over.

Bake at 350 degrees F for 1 hour. When cool, sprinkle powdered sugar over top.