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Preheat oven to 350F. Line 18 muffin cups with paper liners.
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In a mixing bowl, whisk together flour, baking soda, baking powder, and salt. Set aside.
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With an electric mixer, beat bananas, sugar, and brown sugar. Add egg and beat until combined. With the mixer running, slowly pour in butter. Add vanilla.
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Slowly add dry mixture, beating just until all the flour is incorporated.
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Divide the batter among the 18 muffin cups, filling about ¾ full. Dollop about a teaspoon of nutella on each one and use a knife to swirl.
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Bake in the preheated oven for 17 - 19 minutes or until golden brown.
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Cool completely on a wire rack before serving.