Make the browned butter. In a saucepan over medium-high heat, melt the unsalted butter. Stir frequently and wait for the butter to bubble, foam and turn golden brown, about 3-4 minutes. It will smell nutty and sweet. Remove from the stovetop and pour the butter into a heat-proof bowl, making sure to scrape any brown bits at the bottom of the pan. Place in the fridge for 10-15 minutes to cool down to room temperature.
½ cup unsalted butter
Preheat the oven to 350℉. In a mixing bowl, add the bananas and mash them with a fork or spoon until no lumps remain and it's a soft mixture. Then add the cooled browned butter, granulated sugar and brown sugar. Whisk together until well combined.
2 large bananas, ⅓ cup brown sugar, ⅔ cups granulated sugar
Then add the eggs one at a time, as well as the cinnamon and vanilla extract. Whisk until combined.
2 eggs, ½ tsp ground cinnamon, 1 tsp vanilla extract
Then add the flour, baking soda and salt. With a rubber spatula, mix until just combined.
1½ cup all-purpose flour, 1½ tsp baking soda, 1 tsp salt
Fill your muffin pan with paper liners, or rub each well with melted butter or canola oil. Fill each well with muffin batter until each one is about ¾ths full.
Using a spoon, add a small dollop of Nutella to the center of each muffin. With a small knife, swirl the Nutella into the batter. Do not overdo it!
¼ cup hazelnut spread
Place the muffins in the oven and bake for 15-20 minutes, until the tops are golden and a knife comes out nearly clean when inserted. Let cool and enjoy!