Heat oven to 350ºF. Melt butter in 3-quart saucepan over low heat. Cook garlic in butter about 1 minute, stirring occasionally, until golden. Stir in flour. Cook, stirring constantly, until bubbly; remove from heat. Stir in milk and broth. Heat to boiling, stirring constantly. Boil and stir 1 minute. Stir in mozzarella cheese, onions, capers, tarragon and lemon pepper. Cook over low heat, stirring constantly, until cheese is melted.