Dissolve yeast in warm water in a medium bowl; let stand 5 minutes. Lightly spoon flour into dry measuring cups; level with a knife. Add flour and salt to yeast mixture; stir until mixture forms a soft dough.
Turn dough out onto a lightly floured surface; knead until smooth and elastic (about 5 minutes). Place dough in a medium bowl coated with cooking spray, turning to coat top. Cover and let rise in a warm place (85°), free from drafts, 35 minutes or until doubled in size. (Press 2 fingers into dough. If indentation remains, dough has risen enough.) Punch dough down; cover and let rest 10 minutes.
Preheat oven to 450°.
Roll dough into a 12-inch circle on a lightly floured surface. Place on a 12-inch pizza pan or baking sheet coated with cooking spray and sprinkled with cornmeal. Bake at 450° for 7 minutes.
Heat oil in a large nonstick skillet over medium-high heat until hot. Add mushrooms and leek; sauté 6 minutes or until mushrooms are golden brown and leek is tender. Sprinkle with thyme and pepper; stir well. Remove from heat.
Spoon pasta sauce over pizza crust. Top with mushroom mixture, and sprinkle with cheese. Bake at 450° for 14 to 16 minutes or until cheese melts and crust is browned. Cut into 8 slices.