Banana Coffee Cake

INGREDIENTS:
CAKE
1 1/2 cup all purpose flour
1 1/2 tsp. baking powder
1/2 tsp. baking soda
1/2 tsp salt
3/4 cup mashed ripe bananas
1/3 cup granulated sugar
1/4 cup brown sugar
1/2 cup sour cream
1/4 cup sour cream
1/4 cup oil
1 egg
2 tsp. vanilla extract
Mix the flour, baking powder, baking soda, and salt together in a bowl and set aside. mix the rest of ingredients in a stand mixer until blended and then gradually add the flour mixture until just combined . pour about 2/3 of the batter into an 8x8 pan lined with parchment paper and sprayed. then sprinkle the cinnamon sugar filling over and then place the rest of the batter on top of the cinnamon mixture.
CINNAMON SUGAR FILLING:
1 tsp. cinnamon
3 tsp. brown sugar
2 tsp granulated sugar
mix together and sprinkle in between the batter.
TOPPING:
3/4 cup all purpose flour
1/3 cup walnuts (optional)
1/2 cup softened or room temperature unsalted butter cut up
1/3 cup brown sugar
3 TBS granulated sugar
1 1/2 tsp. cinnamon
pinch of salt
combine the ingredients together with a pastry cutter or by hand until a crumble is formed and sprinkle the crumble on top of the batter. Bake in a 350 degree oven for 30-40 mins or a toothpick inserted comes out clean.
ICING:
1/2 cup powdered sugar
2-3 TBS milk
mix together and drizzle on the top of your cooled cake!!