1. Preheat oven to 350 degrees. Whisk flour and 1/2 cup milk in saucepan until smooth. Gradually whisk in remaining milk. Bring to a boil over medium heat, whisking constantly, and boil 1 minute, or until thickened. Remove from heat; stir in pesto, Parmesan, salt and pepper. Reserve 1 cup white sauce.
2. Warm oil in large nonstick skillet over medium-high heat. Add chopped asparagus (not tips) and cook, stirring often, 5 minutes, or until tender. Add garlic; cook, stirring, 1 minute, and season to taste with salt and pepper. Remove from heat.
3. Coat 13x9-inch baking dish with cooking spray. Place layer of noodles in dish, overlapping slightly. Layer with half of cooked asparagus, 3/4 cup Fontina and half of sauce. Add another layer of pasta, remaining sauce, remaining cooked asparagus and 3/4 cup Fontina. Top with layer of noodles, then with reserved 1 cup white sauce. Arrange reserved asparagus tips over top and sprinkle with remaining Fontina.
4. Bake, uncovered, 35-40 minutes, or until golden. Let stand 10 minutes; serve with additional grated Parmesan cheese, if desired.