Combine oil and garlic in a large Dutch oven over low heat. Cook 10 minutes or until garlic is golden and fragrant, stirring often. Lightly coat Dutch oven and garlic mixture with cooking spray. Increase heat to medium-high; add tempeh, and sauté 8 minutes or until brown. Stir in wine; cook until liquid is almost evaporated (about 30 seconds). Transfer tempeh mixture to a bowl.
Return pan to medium-high heat. Recoat pan with cooking spray. Add leek and mushrooms; sauté until vegetables begin to brown and liquid is almost evaporated (about 10 minutes). Add 1 cup broth; cook 1 minute, scraping pan to loosen browned bits. Combine remaining 2 cups broth and flour in a small bowl, stirring well with a whisk. Add broth mixture to pan. Reduce heat, and stir in tempeh mixture. Cover; simmer 30 minutes. Stir in thyme, salt, and pepper. Remove from heat; stir in parsley.