In a blender or food processor, chop the walnuts until they are a fine powder.
Next, add the garlic cloves, salt, olive oil, lemon juice, and arugula and blend until the pesto is a thick paste. You can add more oil as needed.
Assembling The Pizza
Spread the pesto onto the pizza dough using a baking spatula.
Evenly space out the mozzarella balls over the top of the pizza and sprinkle the sausage and mushrooms in between the cheese. Sprinkle with cracked pepper if desired.
Bake for 20 minutes or until the cheese has melted.
Remove from the oven and top with fresh arugula. Cut into slices and serve!