Preheat the oven to 200°C. Peel the potatoes and sweet potatoes, cut them into roughly 2 cm cubes, and place them in salted water to boil. Cook for 15–20 minutes until tender. Peel and grate the garlic (or use a garlic press).

Drain the potatoes and mash them with a fork or potato masher. If desired, add a little butter or milk (optional). Season with salt and pepper.

Heat a little oil in a pan. Add the ground meat and cook over medium heat for about 4–5 minutes. Then add the garlic and cook for another 4–5 minutes. Season with salt and pepper.

Add soy sauce and tomato paste to the pan and fry for a few more minutes. Then add the tomato sauce, vegetable stock, and a little water. Stir and bring to a boil, then reduce the heat and simmer for 15–20 minutes until thickened. Adjust seasoning with salt and pepper if needed.

Spread the ground meat mixture evenly in a baking dish greased with butter. Then add an even layer of mashed potatoes on top, and sprinkle grated cheese over everything. Bake in the oven for 15–20 minutes until the cheese is nicely golden.

Serve the sweet potato pie with fresh arugula.