Peel and slice the potatoes thinly, so they cook evenly. Set them aside in a bowl of water to prevent browning.

Peel and grate the carrot using a box grater or food processor. The carrot adds sweetness and color to the dish.

Finely chop the onion and mince the garlic cloves. These aromatics will enhance the flavor of the béchamel sauce and the vegetables.

Wash the spinach thoroughly and roughly chop it if the leaves are large.

In a large pan, heat 1 tablespoon of olive oil over medium heat. Add the chopped onion and garlic, and sauté until they are soft and fragrant, about 5 minutes.

Add the grated carrot and continue to sauté for another 3-4 minutes until the carrot softens.

Add the chopped spinach to the pan and cook until wilted. Season with a little salt and set the vegetable mixture aside.

In a medium saucepan, heat the remaining 3 tablespoons of olive oil over medium heat.

Once the oil is hot, add the flour and whisk continuously to create a roux. Cook the roux for 2-3 minutes, ensuring it doesn’t brown.

Gradually add the milk to the roux, whisking constantly to avoid lumps. Continue to cook the sauce, stirring constantly, until it thickens and coats the back of a spoon.

Season the béchamel sauce with salt to taste. If you like, you can also add a pinch of nutmeg for extra flavor.

Preheat your oven to 180°C (360°F).

Grease the bottom of your baking dish with a little oil to prevent sticking.

Start by layering the sliced potatoes at the bottom of the dish, followed by a layer of the sautéed vegetable mixture.

Pour half of the béchamel sauce over the vegetables, spreading it evenly with a spatula.

Add another layer of potatoes and then the remaining vegetable mixture.

Pour the rest of the béchamel sauce over the top, ensuring everything is well coated.

Sprinkle the grated mozzarella cheese over the top.

Place the assembled dish in the preheated oven and bake for 30-35 minutes, or until the potatoes are tender and the top is golden brown and bubbly.

Once baked, remove the dish from the oven and let it cool for a few minutes before serving.