With a homemade crust and a little twist by adding mushrooms, red pepper, and Italian cheese, this crab quiche is extra creamy, light, and smooth. My mom said eating it made her feel like she was in the French countryside. If you don't feel like the hassle of making the crust, use a 9-inch frozen pie crust. Plain mozzarella will work in place of Italian cheese blend, too.
Whisk flour, 1 egg, salt, and baking powder together in a bowl; Add butter-flavored shortening into flour mixture and combine by hand until mixture resembles coarse crumbs. Stir ice water into the mixture, adding enough so the dough just holds together. Form dough into a ball, wrap in waxed paper, and refrigerate 30 minutes.
Preheat oven to 400 degrees F (200 degrees C).
Generously flour a large sheet of waxed paper and roll the dough out to an even circle about 11 inches across; fit crust into a 9-inch pie dish. Press edges of dough gently over rim of crust.
Bake the crust in the preheated oven until lightly browned, 6 to 7 minutes.
Reduce oven heat to 375 degrees F (190 degrees C).
Heat butter in a large skillet over medium heat; cook and stir mushrooms, green onions, and red bell pepper in the hot butter until vegetables soften, about 7 minutes; stir in garlic and cook a few minutes more. Season vegetables with salt and black pepper.
Whisk cream, eggs, celery salt, and hot sauce together in a bowl until thoroughly combined; stir crabmeat and mushroom mixture into egg mixture. Crumble about 3/4 of the herb cheese spread into the bottom of the crust and pour crabmeat mixture over the cheese spread. Crumble remaining herb cheese spread into crabmeat filling and spread Italian cheese blend over the top.
Bake in the oven until crabmeat filling is set and cheese topping is lightly golden brown, 30 to 35 minutes.