STREUSEL:

1/2 c. flour
1/4 c. light brown sugar
1/2 tsp. cinnamon
1/4 c. butter, softened
1/4 c. walnuts, chopped

BATTER:

1/3 c. butter
3/4 c. granulated sugar
1 (8 oz.) container sour cream
2 lg. eggs
1/2 tsp. vanilla
1 3/4 c. flour
2 tsp. baking powder
1/2 tsp. baking soda
1/4 tsp. salt
1 1/2 c. fresh or frozen blueberries

Preheat oven to 350 degrees. Grease a 9 or 9 1/2 inch springform pan. Prepare streusel. In a small bowl, combine 1/2 cup flour, brown sugar and cinnamon, using fork or pastry blender; cut in 1/4 cup butter until mixture resembles coarse crumbs. Stir in walnuts, set aside. Prepare batter. In large bowl with electric mixer beat 1/3 cup butter, granulated sugar, sour cream, eggs, vanilla, 1 3/4 cups flour, baking powder, baking soda and salt to blend. Increase speed to high, beat 5 minutes longer until very smooth, stopping mixer occasionally to scrape down sides of bowl. Pour batter into prepared pan. Scatter blueberries over batter. Sprinkle evenly with streusel mixture. Bake 1 hour until streusel is browned and wooden pick inserted in center comes out clean. Cool cake before removing from pan.