Step 1: Prepare the Meatballs

1. In a large bowl, combine the ground meat, breadcrumbs, egg, minced garlic, diced onion, parsley, Parmesan (if using), oregano, paprika, salt, and pepper. Mix well until the ingredients are evenly combined.
2. Shape the mixture into meatballs, about 1–1.5 inches in diameter.
3. Heat olive oil in a large skillet over medium heat. Fry the meatballs in batches until browned on all sides, about 5 minutes. Remove from the skillet and set aside.

Step 2: Make the Mushroom Stew

1. In the same skillet, melt the butter or heat olive oil over medium heat. Add the sliced mushrooms and sauté until they release their moisture and turn golden brown, about 8–10 minutes.
2. Add the diced onion and garlic, cooking until softened and fragrant, about 2–3 minutes.
3. Sprinkle the flour over the mushroom mixture and stir to coat evenly. Cook for 1–2 minutes to remove the raw flour taste.
4. Gradually add the broth while stirring to prevent lumps. Bring the mixture to a simmer.
5. Stir in the cream, soy sauce, and thyme. Season with salt and pepper to taste.
6. Return the meatballs to the skillet, ensuring they are submerged in the sauce. Cover and simmer for 10–15 minutes, allowing the flavors to meld and the meatballs to cook through.

Step 3: Make the Mashed Potatoes

1. Place the cubed potatoes in a large pot and cover with cold water. Add a generous pinch of salt. Bring to a boil and cook until the potatoes are fork-tender, about 15–20 minutes.
2. Drain the potatoes and return them to the pot. Mash them using a potato masher or ricer.
3. Stir in the milk and butter until smooth and creamy. Season with salt and pepper to taste.

Step 4: Assemble and Serve

1. Spoon a generous portion of mashed potatoes onto each plate.
2. Top with the meatball mushroom stew, ensuring each serving gets plenty of sauce.
3. Garnish with chopped parsley and serve immediately.