Preheat the oven to 350F. Lightly grease two 8 x 4” bread pans or line with foil. Mash bananas; Set aside.
In a medium mixing bowl, whisk together all-purpose flour, whole-wheat flour, baking soda, salt and cinnamon.
In a stand mixer bowl fitted with the paddle attachment, cream together butter, granulated sugar and brown sugar until light and fluffy. Add eggs, mixing until incorporated. Add Greek yogurt, vanilla extract and banana mixture. Mix on low until well combined.
Add dry ingredient mixture to wet mixture, mixing by hand until flour is incorporated. I like to do this with a wooden spoon. Avoid overmixing.
Make crumb topping by combining flour, sugar and cinnamon in a small bowl. Cut in cold butter with a pastry cutter until topping looks like coarse crumbs.
Divide banana bread batter evenly into baking pans. Sprinkle half of the streusel topping on each loaf. Bake in preheated oven for 35-45 minutes or until toothpick comes out clean.