Blueberry and Sour Cream Crumb Coffee Cake

Last week I made delicious blueberry muffins, but still had a ton of blueberries left over. So I went on a search to find a recipe to use them with. I know Zak likes sour cream-blueberry pie, but that option was eliminated once I discovered we didn't have enough graham crackers to make a pie crust, and I didn't have the car to go grab a pie crust. Instead, I found this wonderful recipe on recipezaar, one of my favorite cooking websites. This recipe was absolutely delectable and will be a keeper!

Filling
1/2 lb. blueberries (I probably used a bit more than 1/2 lb.)
2 Tbl. sugar
2 Tbl. cornstarch

Crumbs
1/3 c. brown sugar
1/3 c. sugar
1 tsp. cinnamon
1/8 tsp. salt
1/2 c. butter, melted
1 3/4 c. flour

Cake
1/3 c. sour cream
1 egg
1 egg yolk
2 tsp. vanilla
1 c. flour
1/2 c. sugar
1/2 tsp. baking soda
1/2 tsp. baking powder
1/4 tsp. salt
6 Tbl. butter, softened, cut into 6 - 8 pieces

1. Preheat oven to 325-degrees.
2. Toss together the filling ingredients.
3. Whisk together all of the crumb ingredients, except the flour (brown sugar, sugar, cinnamon, salt, melted butter) until smooth.
4. Add the flour in--the dough will look solid.
5. In a small bowl, mix together sour cream, egg, egg yolk and vanilla.
6. In mixer, add flour, sugar, baking soda, baking powder and salt.
7. Add butter and one spoonful of sour cream mixture until moist-mix for about 30 seconds.
8. Add remaining sour cream mixture, in two batches, mixing for 20 seconds each time.
9. Reserve 1/2 c. of entire cake batter mixture.
10. Pour the rest of batter into an 8x8-inch pan.
11. Add blueberries, then 1/2 c. of reserved mixture.
12. Sprinkle crumbs over top-should be about 1/2" - 3/4" in size.
13. Bake for 45 - 55 minutes. Cool completely.