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1
Preheat the oven to 350u00b0F and line a muffin tin with 4 paper liners.
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2
In a small bowl, sift together the flour, cocoa powder, baking soda, baking powder and espresso powder.
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3
In a medium bowl, whisk together vigorously the oil, vanilla, and brown sugar. Using a spatula, add the dry ingredients to the wet in two batches, alternating with the buttermilk.
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4
Divide the batter between the muffin cups and bake 15-17 minutes, or until a toothpick inserted comes out clean. Let cool completely on a wire rack before proceeding.
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5
While they are cooling, make the filling/frosting. Stir together the Nutella and sour cream and set aside.
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6
Snip off the corner of a plastic bag or pastry bag and place it in a tall glass. Put a metal round tip over the corner that you snipped off. Add the Nutella-sour cream mixture and squeeze it down in the bag towards the tip.
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7
Gently poke a hole in the top of each cupcake and pipe in the mixture. If you don't want to take the time to pipe the filling in, simply spread the mixture on top of each cupcake evenly. Let it firm up for a few minutes in the fridge before frosting.
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8
Next, beat the heavy whipping cream and espresso powder until soft peaks form. Add the cocoa powder and powdered sugar (start with 1 tablespoon, add more to taste).
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9
Frost the cupcakes with the whipped cream mixture using a knife or another pastry bag fitted with a tip for a decorative look.
