(If using store bought pizza dough, skip to step #3) In a large bowl, add warm milk, yeast, and sugar. Whisk together and allow to bloom until foamy, about 10 minutes. Then add flour, milk, olive oil, and salt. Knead together until a dough forms and allow to rise in a warm place for 1-2 hours, until dough doubles in size.
Roll dough out onto a lightly floured surface into a circle until dough is about ½ inch thick. Add parchment paper to a large baking sheet or pizza stone and lay pizza dough on top.
Preheat oven to 450 °F.
In a skillet over medium low heat, add tomato sauce, garlic, Italian seasoning, a dash red pepper flakes, and salt and pepper, to taste. Cook until sauce begins to thicken slightly, about 5-8 minutes. Pour on top of pizza crust, leaving about an inch of the outside of the crust bare.
Top with mozzarella and pepperoni. Bake for 15-20 minutes, until crust has browned and pepperoni has become crisp. Remove from oven and reduce over temperature to 400 degrees F.
Slice mushrooms and toss in salt, pepper, olive oil, and garlic powder. Lay flat onto a baking sheet and roast mushrooms in the oven for 10-15 minutes, until mushrooms have softened. Add mushrooms on top of pizza and eat up! :)