While water comes to a boil, drain defrosted frozen chopped spinach by wringing it dry in a kitchen towel, working over a garbage bowl or your sink. Heat a medium skillet over medium heat. Add extra-virgin olive oil, 2 tablespoons or 2 turns of the pan, and the garlic. Saute garlic in oil 1 minute, then sprinkle spinach into the garlic oil. Add artichoke heart pieces to the pan and turn to combine and heat through. Season vegetables with and remove from heat to a bowl. Place skillet back on the heat and melt butter. Whisk flour into butter and cook 1 to 2 minutes. Whisk stock into flour and butter and let it bubble. Whisk in cream and Parmesan. Season sauce with nutmeg, salt and pepper and thicken 1 to 2 minutes.
Preheat broiler to high. Set rack between middle of oven groove and top rack groove, about 8 inches from heat.
When water boils, salt water, add ravioli and cook 4 to 5 minutes. Ravioli should be less than al dente, still a bit chewy -- it will continue cooking when combined with sauce and vegetables. Place a colander over ravioli as it cooks and add asparagus to it. Cut thin, trimmed asparagus into 2-inch pieces on an angle. Steam the chopped asparagus while pasta cooks, 2 to 3 minutes, until just fork-tender, but still green. Remove asparagus and add to bowl with spinach and artichokes. Place colander in your sink and drain ravioli.
Drizzle a touch of extra virgin olive oil onto the bottom of a medium flameproof oval casserole or a flameproof rectangular baking dish and brush pan to coat evenly. Arrange a layer using 1/2 of cooked ravioli in the dish. Layer 1/2 of the cooked vegetables over the ravioli. Next, add a few ladles of sauce, then vegetables, then top casserole with the last of the ravioli. Dot top of "lasagna" with any remaining sauce and cover liberally with gratedprovolone or 4 cheese blend. Brown cheese 8 inches from broiler, 5 minutes.