For dough: combine 1 1/2 cups flour, yeast and salt in large mixing bowl. Add water and 2 tablespoons oil. Beat with an electric mixer on low speed 30 seconds or until combined. Beat on high speed 3 minutes. Stir in as much of the remaining flour as possible. Turn dough onto lightly floured surface. Knead in enough remaining flour until dough is smooth and elastic, about 7 minutes. Place dough in lightly oiled bowl; turn to oil top. Cover; let rise in warm place until doubled in size, about 40 to 50 minutes.

For filling: Heat 1 tablespoon oil in large skillet over medium heat. Add onion and garlic; cook and stir 4 minutes, or until onion is tender. Add mushrooms; cook and stir 2 minutes, or until mushrooms are tender. Add spinach; cook and stir until spinach is wilted. Remove from heat; stir in mozzarella and Parmesan cheeses.

Preheat oven to 400°F. Turn dough onto lightly floured surface; punch down to remove air bubbles. Divide dough into fourths. Let dough rest 10 minutes. Pat or roll dough into four 6-inch circles. Spread 2 tablespoons sauce on half of each dough circle leaving a 1-inch border. Top each half with sauce, evenly with spinach filling. Moisten edges of dough with water. Fold dough over filling to make four half-moons. Seal edges by pressing with tines of a fork. Prick tops. Place on greased baking pan. Bake 20 minutes, or until golden brown.

Let stand 5 minutes. Serve with remaining pizza sauce that has been heated.