On a cookie sheet with wax paper, scoop a heaping Tablespoon of Nutella. Scoop 12 dollops on a cookie sheet spread out. Freeze for 1 hour until solid.
⅔ cup Nutella
In a large bowl, sift the flour, cocoa powder, baking powder, and baking soda together. Add in the salt and sugar. Set aside.
2 cups All-purpose flour, ½ cup Unsweetened cocoa powder, 2 ½ teaspoon Baking powder, ½ teaspoon Baking soda, ½ teaspoon Salt, 1 cup White granulated sugar
In a small bowl, mix the melted butter, sour cream, vanilla, eggs, and buttermilk
½ cup Unsalted butter, ½ cup Sour cream, 1 teaspoon Pure vanilla extract, 2 Large eggs, ¾ cup Buttermilk
Pour the wet ingredients into the dry ingredients and use a rubber spatula to mix until just combined. Don't over mix! Cover and let sit for 30 minutes.
Preheat the oven to 400°F. Line a 12 cup muffin pan with muffin liners. TIP: The best way to get extra domed muffin tops is to only add batter to every other muffin cup.
Use a small cookie scoop and scoop 1 dollop of muffin batter into each muffin liner. Place a frozen Nutella drop firmly into the batter. Scoop another dollop of muffin batter on top. Spread until even.
Use a teaspoon and scoop 1 teaspoon of Nutella on top of the muffins. Use a butter knife to lightly swirl it on top.
Bake for 6 minutes at 400°F. Then, lower the temperature to 350°F and bake for 10 more minutes.
Let the muffins sit in the hot pan for 10 minutes before placing on a cooling rack.