Chocolate cupcakes

1. Preheat the oven to 350°F/180°C and line a cupcake pan with paper liners.
2. In a bowl, mix and sift together the dry ingredients: flour, unsweetened cocoa powder, salt, and baking soda (or baking powder).
3. In another large bowl, combine the remaining ingredients: vegetable oil, sugar, eggs, vanilla, and milk, and whisk until smooth.
4. Add the dry ingredients and gently fold them in with a hand whisk until you have a smooth batter.
5. Pour the batter into the paper liners, filling them only halfway.
6. Bake in the oven for about 15-20 minutes (without opening the oven door) until they are puffed up; check for doneness by inserting a toothpick into the center, it should come out clean.
7. Let the chocolate cupcakes cool slightly before gently removing them from the pan and allowing them to cool completely on a wire rack.
8. Once completely cooled, remove the center using a cupcake corer or an apple corer and fill with Nutella.

Nutella Mascarpone Frosting

1. Place all the ingredients in a large bowl: cold mascarpone, cold heavy cream, powdered sugar, vanilla, unsweetened cocoa powder, and Nutella.
2. Using an electric mixer on low speed, beat for about 2 minutes until you have a smooth and firm frosting.
3. Fill a large piping bag fitted with a 1M or similar tip with the Nutella frosting and decorate the tops of the cupcakes by piping swirls; sprinkle with crushed hazelnuts and refrigerate for about 1 hour before serving.