Preheat your oven to 360°F (182°C). Grease a 9x5 inch loaf pan and line it with parchment paper to prevent sticking. This will make it much easier to remove the banana bread after baking.

In a medium bowl, combine 1/2 cup flour, 1/2 cup brown sugar, and 1 teaspoon cinnamon. Add 1/4 cup butter and rub it in with your fingertips until the mixture forms coarse crumbs. Place the bowl in the refrigerator until you’re ready to use it. I find refrigerating the topping helps keep the crumbs crisp during baking.

In a large mixing bowl, stir together 1 3/4 cups whole wheat flour, 1/4 cup cornstarch or extra whole wheat flour, 2 teaspoons ground cinnamon, 1 1/2 teaspoons baking powder, and 1/4 teaspoon salt until well combined.

In a large measuring jug or bowl, whisk together 2 large eggs, 1 cup mashed ripe banana, 3/4 cup granulated sugar (or 1/3 to 1/2 cup for less sweetness), 1/3 cup oil, and 1/2 cup plain Greek yogurt until smooth and well blended.

Pour the wet ingredients from Step 4 into the bowl with the dry ingredients from Step 3. Gently fold everything together just until the flour is moistened; it’s fine if a few lumps remain. Do not overmix, as that can make the bread dense. Pour the batter into the prepared loaf pan and evenly sprinkle the chilled crumb topping from Step 2 over the surface. I like to use a fork to gently spread out any bigger clusters for an even bake.

Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean. Allow the bread to cool in the pan for 10 minutes, then carefully remove it from the pan and transfer to a wire rack to cool completely. Don’t forget to peel off the parchment paper before slicing and serving. I always let banana bread cool fully—this gives it the best texture and makes slicing easier.