This yummy cake comes from one of my favorite food blogs: www.foodiefarmgirl.blogspot.com.
Makes One 8-Inch Square Cake
1-1/2 cups semi-sweet chocolate chips
2/3 cup (packed) golden brown sugar
2/3 cup chopped walnuts (optional)
2 teaspoons ground cinnamon
1/2 cup (1 stick/4 ounces) butter, softened (or 1/2 cup trans-fat free margarine, such as Earth Balance)
3/4 cup granulated sugar
1 large egg
1-1/4 cups mashed, very ripe bananas (they cannot be too ripe)
2 Tablespoons yogurt or sour cream
1 Tablespoon milk
1-1/2 cups all-purpose flour
3/4 teaspoon baking soda
3/4 teaspoon baking powder
1/2 teaspoon salt
Heat oven to 350 degrees (325 if using a glass pan such as Pyrex). Grease an 8"x8"x2" baking pan. In a small bowl, combine chocolate chips, brown sugar, walnuts (if desired), and cinnamon; set aside.
In a large bowl, beat butter, sugar, and egg with an electric mixer until fluffy (I use a hand held mixer). Add bananas, yogurt, and milk, and mix well. On low speed, beat in flour, baking soda, baking powder, and salt just until blended.
Spread slightly more than half of the batter in the pan. Sprinkle with half of the cinnamon streusel. Carefully spread the remaining batter over the streusel and then top with the rest of the streusel. Bake until a toothpick inserted in the center of the cake comes out clean, about 40 to 50 minutes. Cool in pan on a wire rack. Serve warm or at room temperature.
This cake tastes even better the next day, and it freezes beautifully. You can freeze the cake whole or cut it into pieces, wrap them tightly in plastic, and place them in a zipper freezer bag. Defrost at room temperature--or in the microwave.