Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
Slice croissants horizontally, leaving one edge connected like a book.
Spread 2 tablespoon Nutella on each croissant bottom half.
Add banana slices (6–8 rounds per croissant).
Sprinkle optional chocolate chips or hazelnuts.
Close croissants gently, avoiding overflow.
Brush tops with egg wash for shine (optional).
Bake 8–10 minutes until golden brown and warm.
Cool for 2–3 minutes before serving.
Dust with powdered sugar and serve warm.