In a medium saucepan, combine milk, cream cheese, flour,salt, pepper, garlic powder and cayenne, if desired. Cook overmedium-high heat, stirring, until mixture comes to a slowboil, 5 to 7 minutes.
Remove pan from heat; stir in remainingcheeses and mustard until cheese melts. In a bowl, tosspasta with cauliflower; pour cheese mixture over top; stir.Divide pasta evenly among 7 bowls; serve immediately.