Peel the potatoes, dice them and put them to boil in salted water.
Finely chop the onion, garlic, and fresh parsley. Heat the olive oil in a smaller pot, then sweat the onions for a few minutes until they begin to soften. Add the garlic, stir, and just as you can smell the garlic aroma, pour in the tomato passata and add a bit of salt and pepper. If the passata is a bit sour, you can add a teaspoon of sugar to balance it out. Let the sauce bubble until reduced.
Heat a bit of olive oil in a frying pan, then add the dumplings and fry them on medium heat for 5-7 minutes, flipping occasionally. After that, pour the tomato sauce over the dumplings, stir, add the fresh parsley and let cook for a few more minutes.
When the potatoes are boiled, add the butter, pour in the milk and add a bit more salt (as needed), then mash the potatoes.
Serve the mashed potatoes on a plate, add the dumplings and pour the sauce over them.