1. Cook pasta according to package directions, omitting salt and fat; drain. Set aside.
2. Preheat broiler to high.
3. Heat a Dutch oven over medium heat. Add oil to pan; swirl to coat. Add garlic to pan; cook 3 minutes or until garlic is fragrant, stirring frequently (do not brown). Stir in 1 cup stock; bring to a boil. Cook 1 minute. Combine remaining 1 1/4 cups stock, milk, and flour; stir with a whisk until flour dissolves. Add milk mixture to garlic mixture, stirring with a whisk. Bring to a boil; cook 5 minutes or until mixture begins to thicken. Remove milk mixture from heat; add cream cheese, stirring until smooth. Stir in salt and pepper. Add cooked pasta to milk mixture, tossing to coat. Let stand 5 minutes. Pour pasta mixture into a 2-quart baking dish coated with cooking spray. Sprinkle cheddar evenly over pasta mixture. Broil 3 minutes or until cheese melts and begins to brown. Let stand 5 minutes.