Preheat oven to 425°F (218°C). Spray a 12-count muffin pan with nonstick spray or line with cupcake liners. Set aside.

Mix all the streusel ingredients together in a small bowl. Set aside.

Whisk the flour, cinnamon, baking soda, baking powder, and salt together in a medium bowl. Set aside.

Using a handheld or stand mixer fitted with a paddle attachment, beat the butter and sugar together on medium-high speed in a large bowl until creamed, about 3 minutes. Scrape down the sides and bottom of the bowl as needed. (Here’s a helpful tutorial if you need guidance on how to cream butter and sugar.) Add the egg and beat until combined, about 1 minute. Scrape down the sides and bottom of the bowl as needed. Add the mashed bananas and yogurt, and then beat on high speed until combined; mixture will look curdled and that’s ok.

Add the dry ingredients and beat on low speed until combined. Batter is thick. Do not overmix.

Layer a large spoonful (about 1.5 Tablespoons) of batter into each muffin cup. Sprinkle with 1 scant Tablespoon of streusel. Layer another large spoonful of batter over each, using up the remaining batter, then finish by sprinkling remaining streusel on top of each muffin. The 12 muffin cups should be filled all the way to the very top. With a toothpick or knife, gently swirl the streusel topping with the batter.

Bake for 5 minutes at 425°F, then, keeping the muffins in the oven, reduce the oven temperature to 350°F (177°C). Bake for an additional 15–16 minutes or until a toothpick inserted in the center comes out clean. The total time these muffins take in the oven is about 20–21 minutes. Allow the muffins to cool for 5 minutes in the muffin pan, and then transfer to a wire rack to continue cooling, or enjoy warm.

Muffins stay fresh covered at room temperature for a few days, then transfer to the refrigerator for up to 1 week.