Step 1

Preheat oven to 350 degrees. Line a baking sheet with parchment paper or a silicone mat. Working with one sheet of puff pastry at a time, unfold it on a lightly floured surface. Following the seams in the puff pastry, cut the sheet into thirds.

Step 2

Cut each third into two triangles by cutting between two opposite corners to make six long, skinny triangles. Repeat with second sheet of puff pastry until you have 12 triangles. Spread 1 tablespoon Nutella on the widest part of each triangle. Top with 3 banana slices.

Step 3

Starting at the wide end of the triangle, roll the pastry up so the tip of the pastry is underneath the croissant. Arrange on prepared baking sheet and repeat with remaining triangles.

Step 4

Brush the tops of the croissants with the egg and water mixture. Place in oven and bake until the croissants are fragrant and golden brown, 30 to 40 minutes. Remove from oven and cool 5 minutes. Serve warm or at room temperature.