Heat the oil in a large, non-stick sauté pan over medium heat. Once the oil is hot, add the mushrooms and season with 1 teaspoon of the salt and pepper. Cook in an even layer, stirring occasionally, until most of the moisture has cooked out of them, 12 to 15 minutes. Remove from the heat and set aside.
Meanwhile, use a cookie cutter (preferably star or snowflake-shaped) to punch out shapes into the bread slices. Tear the leftover bread scraps into roughly 1”-inch pieces and place them in an even layer on the bottom of a greased 9x13”-inch baking dish.
Next, sprinkle half of the vegan mozzarella on top of the bread scraps. Then, layer on half of the tomato slices, followed by all of onions and reserved sauteed mushrooms.
Sprinkle the remaining mozzarella shreds over the mushrooms, then layer on the star-shaped bread slices, followed by the rest of sliced tomatoes.
Last, whisk together the JUST Egg, non-dairy milk, smoked paprika, dried oregano and basil, and garlic powder, until thoroughly combined. Pour the mixture evenly over the casserole, and top with the olives and parmesan shreds. Cover with cling wrap, and refrigerate overnight, or at least 6 hours.
About 15 to 20 minutes before you’re ready to bake it, preheat the oven to 325°F. Uncover the strata and bake uncovered in the preheated oven until the strata is puffy and golden-brown, 60 to 75 minutes.
Allow to cool at room temperate for 10 to 15 minutes. Serve with fresh minced parsley and enjoy