To make this breakfast bake, start by preheating your oven to 350 F.
Next, grease a 9x12 baking dish with oil, butter, or cooking spray, and set it aside.
Then, prepare the spinach. Thaw the frozen spinach according to the package instructions and use a paper towel to squeeze out as much moisture as possible. Once it's done, set it aside.
Next, prepare the eggs. Crack the eggs into a large bowl and add in the kefir. Whisk until they're smooth, then add in 1/4 cup of the parmesan cheese and whisk again until fully combined. Set aside once done.
Heat a large skillet, on the stove, over medium heat, and add in the olive oil.
While the oil is heating, finely dice the onion and garlic.
Once the oil is hot, add the diced onion and garlic to the pan, and sauté for 3-4 minutes, until the onions begin to soften.
Then, add in the Italian sausage, using a spoon to break it down into small pieces. Sauté until the sausage is cooked through.
Then, add the thawed spinach to the pan and cook everything together for another 3-4 minutes.
Once the spinach and sausage mixture is cooked through, remove them from the heat and drain any excess liquid from the pan. Stir in the ricotta cheese, then set the mixture aside.
Next, prepare the english muffins. Slice them in half, and add one half of each muffin to the bottom of the greased baking dish.
Scoop the spinach and sausage mixture on top of the muffins until all of it has been used.
Then, place the remaining halves of the english muffins on top of the spinach and sausage mixture and press it down until a sandwich forms.
Finally, pour the egg mixture evenly across the tops of the muffins, ensuring that they are fully covered and none of the muffins are exposed. Sprinkle the remaining parmesan cheese on top.
Transfer the baking dish into the oven and allow it to bake for 35-40 minutes, until the eggs are set and the top is golden brown.
Once it's done, remove it from the oven and allow it cool for five minutes. Then, slice, serve, and enjoy!