Break the cauliflower into pieces and steam until crisp tender. In a large bowl combine the garlic, cheeses(reserving a 1/2cup of the cheddar) and milk. Gently stir in the cauliflower. Spread in a 9x13 pan. Bake covered in foil for 25 minutes. Remove the foil and bake 10 more minutes until the cheese is bubbly.