Start by making the egg pasta. On a work surface, mound the flour and make a well in the center. Crack the egg into a small bowl and beat it well—this will help your pasta turn out smoother and finer. Make sure the egg is at room temperature so it combines better with the flour.

Pour the egg into the center of the flour well and begin to mix in the flour with a fork. Once the egg is no longer at risk of spilling over, start kneading by hand. When you have a smooth, elastic dough, shape it into a ball, wrap it in plastic wrap, and let it rest in the refrigerator for about 1 hour.

In a separate bowl, combine the mashed potato and finely chopped meat with a pinch of salt. Mix well to make the filling.

After the dough has rested, take it out and flour your work surface. Roll out the dough with a rolling pin, always starting from the center and working outward. Only flour the dough, not the rolling pin, to prevent sticking. Rotate the dough 180 degrees and keep rolling until you have a very thin sheet; when you think it's thin enough, roll it even thinner!

Once the dough is rolled out, place small mounds of filling at regular intervals (I use a round cutter to mark the edges). Moisten the edges of the ravioli, lay another sheet of dough on top, and form the ravioli one by one, pressing out the air and sealing the edges well. Now your ravioli are ready.

Make a light tomato sauce: finely chop the onion and sauté it in a little olive oil. Add the tomato sauce, salt, and pepper, cover, and cook for about 20 minutes.

Bring a pot of water to a boil and cook the ravioli for about 5 minutes. Remove them with a slotted spoon (not a colander, as they might break) and transfer them to the pan with the sauce. Toss quickly and serve. Garnish with fresh basil.