1. In large saucepan cook onion in hot butter over medium heat until tender. STir in potatoes, cider, thyme, salt, and cayenne pepper. Bring to boiling; reduce heat. Simmer, covered, 15 minutes. Add chopped apple; simmer, covered, 5 minutes or until potatoes are tender.
2. In small bowl combine flour & milk; stir into soup. Cook & stir until bubbly. Slowly add cheese, whisking until cheese is melted.
3. Divide soup among serving dishes; top with apple slices & peppercorns.