Chocolate Hazelnut Cupcakes with Nutella Buttercream

Name: Chocolate Hazelnut Cupcakes with Nutella Buttercream
Prep time: 20 min
Cook time: 20 min
Total time: 40 min
Cuisine: American
Ingredients: 1/2 cup vegetable oil (substitute canola oil or neutral vegetable oil); 1 cup granulated sugar; 2 large eggs (room temperature); 1 teaspoon vanilla extract; 1/2 cup whole milk; 1 cup cake flour (substitute all purpose flour); 1/4 cup hazelnut flour (substitute all purpose flour ); 1/2 cup unsweetened cocoa powder; 1 teaspoon espresso powder (optional); 1 1/2 teaspoons baking powder; 1/2 teaspoon kosher salt; 1/2 cup Nutella; 1 cup unsalted butter (room temperature); 3 1/2 cups powdered sugar; 1/4 teaspoon kosher salt; chopped hazelnuts (for garnish )