Preparation of the meatballs

1. In a large skillet, heat 1 tbsp olive oil with 1 tbsp butter over medium heat.
2. Add the chopped onion and cook until translucent, about 5 minutes. Stir in the garlic and oregano, then cook for 1–2 minutes more.
3. In a large bowl, mix the ground beef with the sautéed onion, garlic, grated potato, and oregano.
4. Add salt, pepper, chopped parsley, and the egg, then mix well.
5. Shape the mixture into evenly sized meatballs for uniform cooking.
6. Brown the meatballs in a little butter and oil over medium heat until golden.
7. Transfer the meatballs to a plate and keep warm.

Preparation of the sauce

1. In the same skillet, melt 4 tbsp butter. Once melted, add the flour and stir until it turns a nice golden color.
2. Gradually pour in the hot beef stock while whisking to avoid lumps. Cook over medium heat until thickened.
3. Stir in the cream and Dijon mustard, then simmer for a few minutes until the sauce becomes smooth and creamy.

Final step

1. Return the meatballs to the sauce, cover, and let simmer gently for about 10 minutes.
2. Serve hot with pasta or homemade mashed potatoes.