1. Preheat oven to 450°.
2. Place potatoes in a saucepan; cover with water. Bring to a boil. Cook 10 minutes or until just tender; drain. Cool slightly; cut potatoes crosswise into 1/4-inch slices.
3. Heat olive oil in a large nonstick skillet over medium-high heat. Add onion to pan, and sauté 8 minutes or until tender.
4. Roll dough out on a lightly floured surface to a 14 x 10–inch rectangle. Sprinkle cornmeal over a large baking sheet; place dough on baking sheet. Sprinkle mozzarella evenly over dough. Arrange potatoes and onion over mozzarella; top evenly with goat cheese and garlic. Bake in lower third of oven at 450° for 15 minutes or until browned. Sprinkle with thyme; cut into 12 pieces.