Preheat the oven to 375 degrees.
Line a long rectangle cookie sheet with parchment paper.
Cut each piece of string cheese into eight pieces (for a total of 32).
Roll out the crescent rolls on a cutting board and cut along the dotted lines.
Cut each crescent roll in half.
Spoon a teaspoon of pesto sauce on the larger end of the crescent roll.
Place a small piece of string mozzarella cheese on the pesto sauce and roll up the crescent roll.
Create the shape of a tree, starting with the tree trunk. Add two rows of two for the trunk. Then start with a row of seven and work up, using one less crescent roll for each row.
Add one egg white and a teaspoon of water to a small bowl and beat.
Brush egg wash over the top of the Christmas tree and bake for 20-35 minutes or until the crescent rolls are golden brown.
Melt the butter in a small bowl and add the parmesan cheese and parsley and mix.
Brush the butter mixture over the Christmas tree and serve.