Make the meat sauce by heating the oil in a large saucepan. Add the onions and garlic. Saute, until they soften, about five minutes. Add the sausage or plant meat crumbles and saute for a couple of minutes.
Put the plum tomatoes in a bowl and squish them to break with your fingers. Add to the saucepan along with 1 cup of water.
Stir well, bring to a boil, add the oregano, red pepper flakes, salt and ground black pepper to taste. Stir and let the sauce cook for about 15 minutes or until it turns a bright red. Turn off heat and check seasoning. Set aside.
Make the ricotta, by placing the cashews in a food processor with all ingredients except the parsley. Process for a couple of minutes until fairly smooth. Mix in the parsley and pulse until it's mixed into the rest of the ricotta. Set aside.
Preheat oven to 375 degrees Fahrenheit.
In a two-quart baking dish, layer in half the tomato meat sauce. Layer on top half the vegan parm, half the ricotta and half the mozzarella. Repeat one more layer of the tomato sauce, vegan parm, ricotta and mozzarella.
Place the baking dish, uncovered, in the oven and bake 25 minutes. The sauce should be hot and bubbly. If your cheese is not melting, you can try turning on the broiler for 3-4 minutes at the end, but be careful and check frequently because you don't want it to burn.
Remove and serve hot with lasagna chips.