Preheat your oven to 400°F (200°C).

Defrost the puff pastry according to package instructions and place one sheet on a parchment-lined baking sheet.

Gently melt the Nutella using a double boiler or microwave and evenly spread it onto your first pastry sheet.

Place the second puff pastry sheet on top of the Nutella-covered sheet and dust with flour to prevent sticking.

Using a pizza cutter or sharp knife, cut the pastry from the top down towards each corner to form a large triangle.

With the scraps of dough, use a cookie cutter to create star shapes.

Carefully lift and flip the top left side of the dough to connect with the triangle shape, pinching the edges together.

Make cuts along the tree's sides, twisting each piece to create a visually appealing tree shape.

Prepare an egg wash by mixing the egg and water in a bowl. Brush the entire tree, including star shapes.

Bake in the preheated oven for about 20 minutes or until golden brown.

Dust with icing sugar before serving.