Cook the spinach on the stove in a pot over medium heat for 2-5 minutes.
When the spinach is wilted, transfer into a blender with 1/4 cup of water. Blend the spinach into a puree, and set aside.
Dissolve sugar and yeast in warm water. Let the mixture sit for 5 minutes until foamy.
Transfer the yeast mixture, spinach puree, olive oil, salt, and 1 1/2 cups flour into the stand mixer.
Using the dough hook, turn to speed 2 and mix for about 1-2 minutes.
Add remaining flour, 1/2 cup at a time, until dough clings to dough hook and cleans sides of bowl. Knead on speed 5 until the dough is formed together the the sides of the bowl are clean (about 2-3 minutes).
Place dough in a greased bowl and cover until the dough rises and doubles in size (at least 1 hour).
Pull Apart Christmas Tree
Preheat your oven to 425° F.
Transfer the dough onto a floured surface and divided into 22 balls.
Cut the mozzarella cheese block into 22 cubes.
Flatten each pizza dough ball, and place a mozzarella cube in the middle. Take the edges of the dough and bring together to form a ball. Repeat with the remaining dough.
Arrange the balls to form a christmas tree, with 1 ball in the first row, followed by 2 in the second, 3 in the third, 4 in the fourth, 5 in the fifth, 6 in the sixth, and 1 in the last row to form the tree trunk.
Mix the milk and water to create the milk wash, and use a pastry brush to coat the tops of the balls.
Bake the pull apart christmas tree for 18-20 minutes until the top is golden brown.
In a small bowl, mix together the butter, garlic, basil and crushed red chilli flakes.
Brush the pull apart christmas tree with the garlic butter, and top with parmesan cheese.