Keto Egg Strata is a delicious make-ahead breakfast casserole with layers of bread, eggs, spinach, and cheese. Loaded with flavor in every bite, it's the ideal recipe for a special brunch.
Preheat the oven to 325ºF and line the very bottom (only the bottom) of a 9x5 loaf pan with parchment paper. Do not grease the pan at all.
In a large bowl, whisk together the almond flour, protein powder, sweetener, baking powder, and salt. In a medium bowl, whisk together the egg yolks, whole egg, oil, and water. Whisk the egg mixture into the dry ingredients until smooth and well combined.
In another large bowl, beat the egg whites with the cream of tartar until they hold very stiff peaks. Fold the egg whites into the batter until well combined and no streaks remain.
Spread the batter in the prepared pan and bake 40 to 50 minutes, until the top is risen, uniformly golden brown, and springs back when pressed. Remove from the oven and let cool completely in the pan.
Run a sharp knife around the inside of the pan to loosen and flip out. Remove the bottom parchment. Cut into 12 even slices and set on a wire rack over a cookie sheet.
Preheat the oven to 200ºF and place the bread in the oven until hard and dry to the touch, at least 1 hour. Alternatively, you can let it dry out overnight on the counter.
Breakfast Strata
Lightly grease an 8x8 inch glass or ceramic baking dish. Use 2 tablespoons of the butter and spread some on each of the dry slices.
Add the remaining two tablespoons of butter to a medium skillet over medium heat. Add the shallot and sauté until translucent, about 2 minutes. Add the spinach and season lightly with salt and pepper. Stir to combine well with the shallots, then remove from heat.
Arrange half of the bread, buttered side up, in the prepared baking dish. Sprinkle with half of the spinach mixture, then half of the grated cheese. Repeat with the remaining bread, spinach, and cheese.
In a large bowl, whisk together the eggs and cream. Season generously with salt and pepper and pour over the bread in the pan. Cover with plastic wrap and weigh down everything with several heavy cans.
Refrigerate 1 hour or up to overnight, to allow the egg mixture to soak into the bread.
When ready to cook, preheat the oven to 325ºF. Remove the casserole from the fridge, remove the cans and plastic wrap, and let stand at room temperature while the oven is heating.
Bake until puffed and golden brown, and the edges have pulled away from the sides of the pan a bit, about 45 to 55 minutes. Remove and let cool 10 minutes before serving.