Preheat the oven to 400 degrees F (205 degrees C) and line a baking sheet with parchment paper.
Sprinkle some of the All-Purpose Flour (2 tablespoon) on a clean work surface, then use a large bowl to cut a large circle out of the Puff Pastry (1 sheet).
Transfer the pastry to the prepared baking sheet. Press a medium-sized bowl in the center of the pastry to mark the circle in the dough. Using a sharp knife, cut 4 equal cuts into the center circle to create 8 triangles.
Spread the Basil Pesto (1/2 cup) around the outer circle of the pastry. Then sprinkle Italian Sausage (0.75 pound) and Mozzarella Cheese (1 cup). Season with Crushed Red Pepper Flakes (2 teaspoon), Salt (to taste), and Ground Black Pepper (to taste).
Bring one point of the center star over the filling, as well as bringing the outer edge of pastry inwards. Press the two together and continue until you have a wreath.
Brush with Egg (1) then place in the oven and allow to bake for 15 minutes, until golden brown and cooked through.
Remove from the oven. Allow to rest for 5 minutes then slice and serve with pesto sauce.