To prepare the potatoes, boil water in a big saucepan. Add the potato slices and a little teaspoon of salt.
Simmer the potatoes for five minutes or until they are slightly soft. After draining, put away.
Cook the Onion and Spinach: Heat a little amount of vegetable oil in a pan over medium heat.
Add the onion, cut into pieces, and cook until transparent.

Cook the chopped spinach until it wilts and most of the liquid has evaporated, after adding it. Take off the heat.

Put the Casserole Together:

Set a casserole dish aside and gently coat it with vegetable oil while preheating the oven to 350°F/175°C.
Beat the eggs, cream cheese, baking powder, and granulated garlic in a large mixing basin. Add salt to taste to season.
Place half of the boiling potatoes in the bottom of the casserole dish that has been prepared.
Cover the potatoes with the spinach and onion mixture.
Transfer half of the egg mixture over the layer of spinach.
Proceed with the leftover potatoes and combination of eggs.
Evenly distribute the shredded mozzarella over the top.
Bake the casserole for 25 to 30 minutes, or until the top is golden brown and the eggs are set. Bake in a preheated oven.
To serve, let the casserole cool for a couple of minutes. It will set more easily and cut into chunks more easily as a result.
Serve warm, maybe with a simple salad or a side of crusty bread.
Serving Ideas:

You may have this casserole with spinach and potatoes for breakfast or as a major course for supper. It’s a great alternative for family dinners or get-togethers since it goes well as a side dish to a more substantial main course or as a simple green salad drizzled with vinaigrette.

This dish, which is rich, creamy, and full of cozy aromas, is a shining example of the grace and ease of Spanish home cooking. Try it out and add a little bit of Spain to your meal!