Heat oven to 350'F. Spray a shallow rectangular 2-quart baking dish with vegetable cooking spray. In a large nonstick skillet, saute SPAM in butter 3 minutes. Add onion, spinach, and thyme; cook and stir 2 minutes. Set aside. Cut a thin slice off the top of each potato. Scoop out each potato, leaving a 1/2" shell. Place shells in prepared baking dish. Place scooped out potato in medium mixing bowl. Beat at medium speed 30 seconds. Add milk, Parmesan cheese, and pepper; beat just until combined. Stir in SPAM mixture. Fill potato shells with potato mixture. Bake, uncovered, 25-30 minutes or until thoroughly heated. Top with cheeses. Bake 5 minutes longer or until cheese is melted. ~--