Preheat oven to 375° F.
Brown the sausage in a skillet, chopping into small chunks as it cooks. Place a couple of paper towels into a bowl and remove the sausage from the pan into the bowl to soak up the grease. Set aside.
Whisk together eggs, almond milk, salt and pepper.
Layer brad in the bottom of a 13 x 9 baking dish.
Pour butter over the bread. There's not enough butter to saturate the bread, so pour it evenly across the top, drizzling slowly.
Add half of the red onion slivers in an even layer on top of the bread.
Add the sausage and mushrooms in an even layer, one at a time.
Spread spinach out across the top of the sausage and mushrooms and then add the remaining onion on top of the spinach.
Cover the baking dish with aluminum foil and bake for 40 minutes.
While the casserole cooks, mix 1/2 of the Miyoko's cheese wheel with about 1/4 cup of Violife cheddar shreds. Using the back of a spoon, mash them together until they're well mixed.
Remove the baking dish from the oven and set the aluminum foil aside but don't toss it just yet.
Add small dollops of the cheese mixture evenly across the top of the casserole. Place the baking dish back into the oven, uncovered, and continue baking for about 10 minutes. Note that the cheese won't melt the way real cheese would.
Take the casserole out of the oven again. Now that the cheese is warm and soft, you can use the back of a spoon to spread it out across the top just a little more evenly.
Put the casserole back into the oven for another 5 minutes, then remove it, cover it with the foil again and let it cool for at least 10 minutes before serving.
Garnish each slice with thinly sliced tomatoes and a dollop of dairy free sour cream. Enjoy!
Cover the leftovers and store in the fridge for up to 5 days.