Prepare the white garlic sauce. Melt the butter in a small saucepan over medium heat. Stir in the flour and cook for about 1 minute. Gradually whisk in the milk until smooth. Add the minced garlic, salt, and black pepper, then simmer until slightly thickened. Stir in the Parmesan cheese and remove from the heat.
Cook the mushrooms. Heat the olive oil in a skillet over medium heat. Add the sliced mushrooms and cook for 6–8 minutes until golden brown. Stir in the garlic and Italian seasoning during the last minute of cooking. Season with salt and pepper.
Preheat the oven to 475°F (245°C) or according to your pizza dough instructions. If using a pizza stone, allow it to preheat for at least 30 minutes.
Assemble the pizza. Stretch or roll the pizza dough into a 12-inch circle. Spread an even layer of the white garlic sauce over the dough, leaving a 1-inch border. Top with the mozzarella cheese, sautéed mushrooms, and Parmesan cheese.
Bake for 12-15 minutes, or until the crust is golden brown and the cheese is bubbly and lightly browned.
Remove from the oven and let the pizza rest for 2-3 minutes. Garnish with fresh parsley, extra Parmesan, and red pepper flakes if desired. Slice and serve immediately.
