Heat oven to 550 degrees. Prepare the dough for topping as instructed.
Brush the olive oil evenly onto the dough. Sprinkle with minced garlic.
To prepare the mushrooms:
Heat the olive oil and red pepper flakes in a large skillet over medium-high heat. When the oil begins to get hot, add the mushrooms. Leave them in the pan undisturbed until browned on one side, about 2 minutes, then flip and brown on the other side. Season with salt and pepper to taste. Set aside.
To top the pizza:
Sprinkle on 2/3 of the mozzarella cheese. Evenly distribute the mushrooms and spinach. Sprinkle the other 1/3 of the mozzarella cheese followed by the crumbled goat cheese. Season the top of the pizza with sea salt.
Bake 13-15 minutes or until the crust is golden and the cheese is melted and bubbly.
Allow the pizza to cool 3 minutes before slicing. Slice into 6 slices. Drizzle with balsamic vinegar. Serve with more red pepper flakes (optional).