1Heat oven to 450°F. In 10-inch skillet, cook sausage and onion over medium-high heat 5 to 7 minutes, stirring occasionally, until sausage is no longer pink; drain. Stir in mushrooms and 1/2 cup of the pizza sauce; cook until thoroughly heated.
2In medium bowl, stir Bisquick mix, boiling water and oil until dough forms (add additional tablespoon of water if needed). Place dough on surface sprinkled with Bisquick mix; roll in Bisquick mix to coat. Shape dough into a ball; knead about 10 times or until smooth. Roll dough into 12-inch round.
3On ungreased cookie sheet, place dough round. Top half of dough with sausage mixture to within 1 inch of edge. Sprinkle mozzarella cheese over sausage mixture. Fold dough over filling; press edge with fork to seal. Sprinkle with Parmesan cheese.
4Bake 14 to 18 minutes or until golden brown. Remove from cookie sheet to cutting board. Cool 5 minutes before cutting into 6 wedges. Heat remaining pizza sauce; spoon over each serving.