Nutella Cake

Name: Nutella Cake
Total time: 1 h 25 min
Yield: 12 servings
Ingredients: 2 1/2 cups light brown sugar; 8 ounces unsweetened chocolate chopped; 227 grams unsalted butter; 1/3 cup unsweetened cocoa powder; 1/2 cup Nutella; 2 teaspoons instant espresso powder optional; 1 teaspoon baking soda; 4 large eggs at room temperature; 3 cups all purpose flour; 1/4 teaspoon fine salt; 16 ounces unsalted butter at room temperature; 4 cups powdered sugar sifted; 1 cup unsweetened cocoa powder sifted; 1 cup Nutella; 1/2 teaspoon fine salt; edible flowers for decorating