Pre-heat oven to 375 degrees F. Remove and discard the tough lower ends of asparagus spears. Chop the spears to about 2-inch lengths. Toss with the onion or garlic and place into casserole dish. Combine the flour, salt and pepper, and milk, and whisk until no lumps remain. Pour over the asparagus and onion. Cover vegetables with shredded cheese.
Toss breadcrumbs with olive oil and scatter over the casserole. Cover and bake 35-45 minutes, or until bubbly. Serve hot.
Serves 2 as a main dish, 4 as a side dish.
 I keep no-cost breadcrumbs on hand almost all the time. When it looks as though I won't be able to finish a loaf of bread before it starts to grow mold, I slice it into very small cubes and place it in a plastic container in the freezer. For this recipe, I would measure out a cup of breadcrumbs; add some dried oregano, dried garlic powder, salt, and pepper; and toss with olive oil. If the breadcrumbs were still very cold when the casserole went into the oven, I would add maybe 5 more minutes to the cooking time listed.