Step 1 In a large, heavy-bottomed saucepan, melt the butter with the oil over medium heat. Add the meat and brown, stirring frequently, 10 to 15 minutes, careful not to burn.
Step 2 Using a slotted spoon, strain the meat from the pan, leaving the fat (it will seem like a lot of fat, but the fat will be absorbed into the sauce as it slowly cooks). Add the carrot, onion and celery to the pan, stirring until the vegetables are translucent and soft, about 15 minutes. Stir in the garlic.
Step 3Add the tomato paste and cook for 5 minutes to marry the flavors. Stir in the white wine and cook until the wine is reduced, about 5 minutes.
Step 4Stir the meat back into the pan along with the veal stock, thyme, 1 teaspoon salt and one-half teaspoon pepper, or to taste. Gently cook over low heat until the flavors are married, 45 minutes to an hour, stirring occasionally. Serve with the spaghetti and grated Parmigiano to taste.