In a mixing bowl, add melted butter, peanut butter, protein powder, sweetener and vanilla extract. Stir until the mixture becomes homogeneous and smooth. You can also use coconut oil instead of butter.
Add in crushed roasted peanuts. Mix well.
Line the muffin tray with 6 muffin cups then pour the fudge mixture into these cups. Top with unsweetened coconut flakes/flour. Freeze for at least 30 minutes or until set. Enjoy and store the remaining in the fridge until next time you want to eat.