1 Preheat oven to 350°F (175°C). Grease a 12-cup mini loaf pan or line with paper liners and set aside.

2 Make the crumb topping: In a bowl combine 1/2 cup flour, 1/4 cup brown sugar, 1/2 tsp cinnamon and 1/3 cup chopped walnuts. Cut in 3 tbsp cold butter with a fork or pastry cutter until mixture resembles coarse crumbs. Refrigerate while you prepare the batter.

3 Whisk dry ingredients: In a medium bowl, whisk together 1 1/2 cups flour, baking powder, baking soda, salt and 1 tsp cinnamon. Set aside.

4 Cream butter and sugars: In a large bowl, beat the softened butter with granulated sugar and 1/4 cup brown sugar until light and fluffy, about 2–3 minutes.

5 Add eggs and vanilla: Beat in the eggs one at a time, then stir in the vanilla until combined.

6 Fold in bananas and sour cream: Mix in the mashed bananas and sour cream (or yogurt) until just combined.

7 Combine wet and dry: Gently fold the dry ingredients into the banana mixture until just combined. Do not overmix.

8 Stir in walnuts: Fold in 3/4 cup chopped walnuts evenly through the batter.

9 Fill pans: Spoon batter into the prepared mini loaf cups, filling each about 2/3 full. Sprinkle a generous pinch of the crumb topping over each loaf, pressing lightly so crumbs adhere.

10 Bake: Bake for 18–22 minutes or until a toothpick inserted into the center comes out clean and crumb topping is golden.

11 Cool: Let mini loaves cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

12 Finish and serve: Optional—dust with powdered sugar before serving. Serve warm or at room temperature with coffee or tea.