In a bowl, whisk together the flour, cocoa powder, baking soda, and salt.
In a separate bowl, whisk together the sugar, oil, egg, espresso/coffee and vanilla until smooth.
Add dry ingredients to wet and stir/fold in just until evenly incorporated; batter does not need to be perfectly smooth.
Divide batter evenly between prepared muffin cups, filling each about 2/3 of the way, to make 11-12 cupcakes.
Bake in preheated oven for 15-18 minutes, just until a toothpick inserted into the center of one of the cupcakes comes out clean. Cool for about 10 minutes in pan, and then transfer to a wire rack to cool completely before frosting.
In the bowl of a stand mixer fitted with the whip attachment, beat the butter on medium-high speed until fluffy. Decrease speed to low and gradually add confectioner’s sugar and cocoa powder, beating in until incorporated. Increase speed to medium-high and continue to beat until smooth, creamy, and lighter in consistancy. Beat in Nutella, vanilla, and salt until fully incorporated.
Using an offset icing spatula, scoop a large dollop of frosting on top of each cupcake and spread to cover surface of cupcake, keep frosting mounded in center. Holding spatula at an angle, smooth out frosting around sides of cupcake to form a cone base (note that sides don’t need to look perfect since they’ll be covered by sprinkles). Use icing spatula to smooth and level frosting in center.
Cup sprinkles in palm of hand and scoop onto slanted sides of cupcakes. Add a small amount of Nutella to an OXO Silicone Decorating Bottle fitted with the small round tip (or a piping bag fitted with a small round tip) and pipe a squiggle of Nutella onto the center of each cupcake.
Cupcakes can be kept in an airtight container at room temperature for 3-5 days.
*To quickly bring an egg to room temperature, place in a bowl and cover with warm water. Let sit for 5-10 minutes before using.