Buttery chocolate crumb. Nutella frosting. Match made in heaven!
In a small saucepan melt your butter on low heat. Whisk in your milk and set aside to cool.
Preheat your oven to 350F/180C. While butter is cooling, sift all your dry ingredients into a medium-sized bowl. Whisk to combine. Line a 12 tray cupcake man with liners.
Whisk in the sour cream, vanilla and egg into your butter mixture until well incorporated. Make a small well in the middle of your dry ingredients and gently pour in the butter mixture. Using a spatula begin to combine your ingredients until most of the flour is incoporated. Your batter will look chunky and not well mixed. THIS IS OKAY. It should not look like cupcake batter (it will look more like dough).
Immediately pour your hot coffee into the batter and begin to gently combine until the coffee has mostly incorporated into your batter. If there are small clumps that is fine. If you overmix your cupcake batter you will get dense, flat and chewy cupcakes.
Divide the batter evenly into the trays (about 2/3 full). I only made 11 with the batter I had. Bake for 15-18 minutes. I suggest checking at 15 to see if a toothpick comes out clean/some crumbs. Leave to cool in the tray for 5 minutes and then transfer to a wire wrack to cool completely before piping.
Beat softened butter until pale and creamy, about 2 minutes. Add the powdered sugar a 1/4 cup at a time. Add cream. Whip on high speed for 3 minutes. Then add cocoa powder and chocolate hazelnut spread beat until frosting is completely smooth and fluffy. Add a splash of vanilla and a pinch of salt to taste. If frosting feels too soft you can set it in the fridge for 10 minutes or add more powdered sugar for structure.
I added about 3 tbsp of cocoa powder to get a dark chocolate colour (and to balance out the sweetness of the Nutella). However, you can decrease the amount of cocoa powder and increase the amount of Nutella. Note that this will yield a light brown colour.
If you want to enhance the flavour you can add hazelnut extract in lieu of vanilla.
Using too much Nutella can yield a frosting that is quite soft, so you may need to play around with the ratios.
If you want to make this into a cake, double the ingredients and divide the batter between tw0 6-inch cake pans. Baking time will need to be adjusted but aim for around 30 minutes and then go up in 5-minute increments. You can check out my other cake recipes for further details.