Line an 8x8 or 9x9 inch square baking pan with parchment paper.
In a medium saucepan over medium heat, combine Nutella, butter, chocolate and powdered sweetener. Stir until melted and smooth.
Remove from heat and stir in hazelnut flour, protein powder and chopped hazelnuts.
Transfer to pan and press firmly and evenly into the bottom. Use a flat bottomed glass covered with parchment or plastic wrap to help press it in.
Refrigerate until firm, at least 1 hour.
Chocolate Topping:
In a heatproof bowl set over a pan of barely simmering water, combine butter or oil and chocolate chips. Stir until melted. Spread over cooled bars and refrigerate until set, about 20 minutes.
Notes
Food energy: 228kcal Total fat: 21.50g Calories from fat: 193 Cholesterol: 17mg Carbohydrate: 7.63g Total dietary fiber: 3.68g Protein: 4.64g Sodium: 59mg