In a medium bowl, combine the milk and the vinegar, and let stand for at least 5 minutes to “sour”
In a separate bowl, combine flour, sugar, baking powder, baking soda and salt in a large mixing bowl. Whisk egg and butter into the “soured” milk. Pour the flour mixture into the wet ingredients, and whisk it together until the batter is smooth. Mix in the Nutella until fully incorporated.
Heat a large skillet over medium heat and spray with cooking spray. Scoop 1/4 cup of batter for each pancake, and flip when bubbles are covering the surface of the pancake. Flip and cook the other side until it is golden.