In 2-quart nonstick saucepan, stir hot water, 1 1/2 cups milk, 2 tablespoons butter, and the sauce mix and uncooked pasta (from Chicken Helper box). Heat just to boiling, stirring frequently. Reduce heat. Simmer uncovered about 12 minutes, stirring frequently, until pasta is tender. Remove from heat; stir in 1/4 cup pesto. Cover to keep warm. Sauce will thicken as it stands.