In a large skillet saute onions with olive oil for 5-7 minutes. Stir in spinach, season with salt and pepper. Add garlic, stir for 30 seconds more, then add in artichokes and remove from heat.
Transfer the filling into a casserole dish.
In a large bowl whisk eggs with milk, salt, pepper, mustard, thyme and parmesan.
Pour egg mixture on top of the filling and sprinkle with cheese.