Artichoke - Spinach - Mushroom Casserole

Ingredients -- Ovo-Lacto Vegetarian

I got this recipe from a beginner's cookbook, so it is easy to make and also very forgiving of experimentation. Feel free to add crumbled tofu, squash, or TVP for extra protein -- or include your favorite other vegetables such as diced green beans, chopped cauliflower, diced carrots, a drained can of peas or garbanzo or black beans, chopped broccoli, etc. etc. "Bulk it up" if desired, by adding a cup of cooked Quinoa (I like to sear the cooked quinoa in butter first so it's more crispy and less mushy), or perhaps add some kind of keto noodles. Most people like artichoke -- a few don't, in which case you can skip the artichoke hearts. Those are meant to be a treat. Garnish with shoestring fried onions, if desired.

1 jar (6.5 ounces +) marinated artichoke hearts
2x packages (10 ounces each) frozen chopped spinach, thawed, squeezed dry between two plates; or, an equivalent amount of fresh spinach, pan-seared in a little water, also chopped and squeezed dry
1 can (10.5 ounces) condensed cream-of-mushroom soup
1/4 pound mushrooms, diced
1 small onion, chopped fine
1/2 cup sour cream
2 eggs, beaten {or egg substitutes}
1/4 tsp.+ each: dried oregano, nutmeg, white pepper
1/2 tsp. lemon juice
1-2+ cloves garlic, minced/pressed

Dusting / crust

Mix together in a separate small bowl: 1/2 cup Parmesan cheese, 1/2 cup keto flour (such as quinoa or coconut flour), 2 tsp. garlic powder, 1 tsp. ground black or white pepper, other spices as desired

Drain the jar of artichoke hearts, reserving marinade. Place marinade in a wide frying pan and add mushrooms, onion, and garlic. If you wish, add additional vegetables here. Cook over medium-high heat, stirring occasionally, until onion is limp. Remove from heat.
Squeeze the thawed spinach to remove as much moisture as possible. Add the spinach to the mushroom mixture along with the soup, sour cream, eggs, spices, and lemon juice. Here you might add the quinoa or noodles, if desired. At this point add about half the dry dusting / crust mixture. You made about 1 cup of this crust mixture, so you are adding about 1/2 cup here.
Stir the spinach mixture until well blended.
Grease or butter a 9x13 baking pan or shallow 1.5-quart casserole dish. Create a bottom crust for the casserole by dusting it with about half of the remaining dry crust powder mixture (so half of what's left is about 1/4 cup).
Spoon half the spinach mixture into the baking dish on top of the crust. Arrange most of the artichokes on top of the layer and spoon the remaining spinach over them. Arrange the remaining artichokes on top. Dust the top of the casserole with the rest of the crust mixture.
Bake, uncovered, in a 325-degree oven for 35 to 40 minutes, or until the custard is set. Let stand 5 minutes before serving.