Make basil pesto (you can also use store-bought pesto): add all the ingredients for the pesto to a food processor and blend until it becomes a paste but it's still a little bit chunky. Season to taste with salt and pepper. Put it in the fridge.

Take one sheet of puff pastry out of the fridge. Roll it out on a piece of parchment paper sprinkled with flour into a rectangle about 1/8-inch (3-4mm) thick (mine was 10x15 inches (27x38cm) but it can have any dimensions as long as it's a rectangle).

Cut a tree shape in the dough (just a triangle for the tree and a small square for the tree trunk, see photos in the body of the post for a reference). You can do it freehand or cut out a template from a piece of parchment paper. Place the leftover scraps of the dough in the fridge.

If at any point your pastry becomes sticky and hard to work with, put it in the fridge for 5-10 minutes to chill.

Place your pastry with parchment paper on a baking sheet. Spread about 1/2 cup of pesto over the dough.

Take the second puff pastry sheet out of the fridge and roll it out exactly like the first one. Place it on top of the pastry with pesto. Cut out the same shape (it doesn't have to be very precise). You don't have to pinch both parts of the dough together. Reserve the scraps and put them in the fridge.

Now cut horizontal lines in the dough on the left and right side ("branches of the tree"), they should be about 3/4 to 1-inch (2 cm) apart. Do not cut in the middle of the tree from the top to bottom.

Twist each strip creating spirals.

How to use up the remaining dough: I cut out some stars from the dough using a star cookie cutter and baked them with the tree. You can place one star above the tree.

Beat the egg with 1 tablespoon of water. Brush the pastry with the egg wash.

Enjoy!