In 10-inch nonstick skillet, heat 2 tablespoons olive oil over medium-high heat. Add onion, sugar, salt and thyme. Cook 8 to 12 minutes, stirring frequently, until onion is golden brown. Remove onion from skillet; set aside.
Heat oven to 400°F. Spray or grease 15x10-inch or larger dark or nonstick cookie sheet. Unroll dough on cookie sheet; starting at center, press dough into 15x10-inch rectangle.
Brush crust with 1 tablespoon olive oil. Spoon onion mixture evenly over dough to within 1/2 inch of edges. Top with sliced potatoes, Gorgonzola cheese, mozzarella cheese and toasted walnuts. Bake 10 to 12 minutes or until crust is golden brown and cheese is melted.