1. Preheat your oven to 375°F (190°C). Butter a muffin pan or line with paper liners.
2. In a small bowl, stir together milk and lemon juice. In a large bowl, whisk together flour, baking powder, baking soda and salt. In a medium bowl, whisk together milk mixture, butter, sugar and eggs. Stir in mashed bananas; mix well. Pour over dry ingredients; stir just until combined. Drop chocolate-hazelnut spread by spoonfuls over batter; fold and swirl into batter. Don’t overmix.
3. Spoon into prepared muffin pan.
4. Bake for 22 to 24 min or until a tester inserted in the center comes out clean. Let cool in pan for 5 min. Transfer to a rack to cool completely.