Cook the pasta. Bring a pot of water to a boil, salt lightly, and cook pasta until just tender.
Reserve some pasta water before draining. Set aside.
Steam the veggies. In a saucepan, add cauliflower, squash, carrot, onion, and garlic. Pour in enough water to cover the bottom by about 1/2 inch.
Cover and steam on medium until very soft, 10–12 minutes. Drain well.
Blend the sauce. Add the cooked veggies to a blender with milk, cream cheese (or yogurt), olive oil, salt, and optional seasonings. Blend until completely smooth and creamy.
If needed, add 1–2 tablespoons of pasta water to help it blend.
Warm the sauce and melt cheese. Pour the blended sauce back into the pot over low heat. Stir in shredded cheese until melted and silky. Taste and adjust salt if needed.
Combine with pasta. Add the drained pasta to the sauce and stir gently to coat.
If the sauce is too thick, loosen with a little more milk or pasta water until it clings nicely but stays creamy.
Cool slightly before serving. For toddlers, let the pasta sit for 2–3 minutes so it’s warm, not hot. Serve in small portions with a child-safe fork or spoon.