In small saucepan, bring 1/2 cup milk to lukewarm over low heat. Remove from heat, whisk in cornstarch until incorporated. Return to heat and add 1 cup grated cheese. Heat and stir mixture until smooth.
Add remaining milk; combine. Stir in remaining cheese. Mix until smooth. Add garlic, salt, and pepper. Continue heating until hot.
Combine macaroni and sauce in bowl and serve immediately. Makes approximately 1 1/2 Cup sauce. Makes 1 to 2 servings.