Preheat the oven to 350°F, 175°C. Line a 12-cup muffin tin with paper liners or grease lightly.
In a large bowl, mash the bananas until mostly smooth. A few small lumps are fine. Whisk in the brown sugar, granulated sugar, melted butter, yogurt, eggs, and vanilla until the mixture looks glossy and combined.
In a separate bowl, whisk the flour, baking soda, baking powder, salt, and cinnamon. This quick mix helps distribute the leavening evenly.
Sprinkle the dry ingredients over the wet ingredients. Use a spatula to fold the batter together, turning the bowl as you go. Stop when you no longer see streaks of dry flour. The batter will be thick. If you’re adding chocolate chips or nuts, fold them in gently now. Overmixing can make muffins tough, so keep it light.
Divide the batter among the muffin cups, filling each about 3/4 full. If you like a little bakery-style finish, sprinkle the tops with coarse sugar.
Bake for 18 to 22 minutes, until the muffins are golden and a toothpick inserted in the center comes out clean or with a few moist crumbs. If you added lots of mix-ins, you may need an extra minute.
Cool in the pan for 5 minutes. Transfer to a wire rack to cool completely, or enjoy warm. The kitchen will smell like a weekend morning. It’s a nice moment.