Line muffin tins with muffin liners or grease the tin well.
In a medium mixing bowl, whisk together the flour, baking soda, baking powder, and salt.
In large mixing bowl, mix the melted butter and sugar until combined.
Add the eggs, yogurt, and vanilla extract. Mix until smooth.
Stir in the mashed bananas until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix.
Divide the batter evenly among the prepared muffin cups, filling each about ¾ full (about 4 Tablespoons of batter each).
Put a couple of teaspoons of Nutella into the center of each muffin and gently swirl with a knife or skewer, or simply leave it as is.
Bake in the preheated oven for 19-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow the muffins to cool in the tin for about 5 minutes before transferring them to a wire rack to cool completely.
Notes
You can also use this recipe to make jumbo muffins. It will make 7-8 muffins and they will take about 25 minutes to bake. Store muffins in an airtight container at room temperature for up to 3 days, or refrigerate for up to a week. They also freeze well for up to 3 months.For extra chocolate goodness, drizzle a little bit of warmed Nutella over the baked muffins.