Preheat the oven to 180°C
Spread the puff pastry onto a sheet of baking paper
With a knife, cut out a large triangle with a square base, like a Christmas tree
Spread a thin layer of rosso pesto onto it, leaving 2mm around the edges
Cover with thin slices of cured ham
Sprinkle with grated mozzarella
Place the second layer of puff pastry on top, cut it to the same dimensions as the first then press down lightly to properly join the two layers of pastry, especially round the edges
Slice the branches 1 cm wide on the right and left, leaving a 2 cm trunk in the middle
If the puff pastry starts getting too soggy to handle, let it stand for a few minutes in the fridge then continue with the rest of the recipe
Gently twist each branch
Glaze the tree with the beaten egg yolk using a brush
Sprinkle with black and white sesame seeds
Gently take the tree and place it on a perforated baking tray
Bake for 20-25 minutes