1. Preheat oven to 350 degrees F. Spray a 9-by-13-inch pan with vegetable cooking spray.
2. Bring a medium pot of water to a boil over high heat. Add macaroni and stir. Cook for 6 to 7 minutes, drain, and rinse macaroni. Pasta should be slightly firmer than al dente.
3. While water on stove comes to boil, whisk together milk, 1/4 cup water, cornstarch, garlic rub, and salt in a microwave-safe bowl. Microwave on high for 1 minute. Rewhisk and microwave at 1-minute intervals until sauce boils and thickens. It may take up to 5 minutes, depending on your microwave. Transfer the sauce to a large mixing bowl and stir in the simmer sauce, sour cream, Parmesan, ham, and pasta. Mix until evenly blended. Set aside.
4. Add 2 tsp. of the oil to a large nonstick skillet and heat over medium heat. Add bread crumbs and stir until coated with oil and toasted, about 1 to 2 minutes. Transfer bread crumbs to a plate and wipe out pan.
5. Spray pan with vegetable cooking spray and add remaining 1 tsp. oil. Heat over medium-high heat and add shallot. Cook and stir until fragrant and sizzling, about 2 minutes. Add mushrooms and stir to combine. Cook mushrooms for 5 minutes; they should reduce in size and start to brown. Add asparagus and stir to combine. Cook until bright green, about 3 minutes.
6. Add cooked vegetables to the pasta mixture and stir until evenly blended. Transfer the mixture to the prepared baking pan. Sprinkle the bread crumbs over the top. (The casserole can be made to this point in advance; cover and freeze for up to 1 month until needed.)
7. Bake for 18 to 20 minutes, until bubbly. (If frozen, place unwrapped casserole in oven as it preheats, and bake at 350 degrees F for 25 to 35 minutes until heated through and bubbling.)
8. Let casserole rest for 5 minutes before serving. Serve hot.
Source: Fresh Magazine March, April 2010