1. Cook macaroni (see package directions). Meanwhile, in a large saucepan, melt butter over medium heat. Add flour, and stir to create smooth paste; cook 1 minute. Add milk, whisking until sauce thickens and becomes smooth, about 6 minutes (it should be thick enough to almost coat a spoon).
2. Season with salt, pepper, and nutmeg. Slowly sprinkle in cheese until sauce is thick, creamy, and smooth.
3. Pour sauce over macaroni, then toss until well-coated; serve.
How kids can help: Most of this recipe involves heat, so little ones shouldn't lend a hand.