Preheat oven to 375°F. Grease muffin tin or spray lightly with cooking spray.
In medium sized bowl, combine streusel ingredients: ½ cup all-purpose flour, ¼ cup sugar, and ground cinnamon. Add butter, and using a fork, pastry cutter, or fingers, cut in butter until mixture resembles coarse crumbs and will hold together when pinched.
In large bowl, mash bananas. Add eggs, yogurt, ½ cup sugar, oil, and vanilla extract, mixing until well blended.
On top of wet ingredients, add whole wheat flour, 1 cup all-purpose flour, baking soda, baking powder, and salt. Gently mix the dry ingredients together before folding them into the wet ingredients. Stir just until combined.
Divide batter evenly between 16 muffin cups, about ¼ cup batter per cup. Muffin cups should be about two-thirds full; do not overfill or streusel will fall off as they bake. Sprinkle approximately 1 tablespoon of streusel on each muffin, patting lightly so it adheres. If there’s extra streusel, simply add more to each muffin.
Bake 15 minutes or until a toothpick inserted in center comes out clean or with just a few crumbs.
Cool muffins in the pan for 5 to 10 minutes before removing and cooling completely on wire rack.
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Notes
Yield varies depending on the size of your muffin tins. If you are making extra large muffins, adjust baking time.
If desired, use all whole wheat flour, all-purpose flour, or white whole wheat flour, or any combination.