Preheat broiler. Melt butter in a 3-qt. saucepan; add diced ham, sliced green onions, and minced garlic. Sauté until golden. Stir in mashed potatoes, chicken broth, milk, peas, and chopped fresh thyme. Bring to a boil; reduce heat. Simmer 8 minutes or until thickened. Season with salt and pepper. Spoon into 4 broiler-safe bowls. Top with torn dinner rolls; sprinkle with shredded Cheddar cheese. Place bowls on a baking sheet. Broil 3 minutes or until golden brown.