How do I make a traditional Bolognese sauce?

Bolognese sauce, sometimes called Bolognese Ragu has many variations, so I will provide the most common method. Dice one brown onion and then sauté in 25g of butter and 4 tablespoons of olive oil. Once the onions start to colour add 35 grams of diced pancetta and let the fat render. Add a mix of 1 chopped carrot, 1 chopped celery stick and 1 diced clove of garlic, stirring for 3-4 minutes. Add 500g of ground beef, seasoning the beef with salt and pepper. Next evaporate 1 cup of red wine, making sure the mixture reduces. Then evaporate 3/4 of a cup of fresh milk, also reducing the mixture. Add 4 chopped and peeled fresh tomatoes, 1 bay leaf and 1/4 tsp of chopped fresh thyme leaves and then simmer the sauce on low to medium heat for 1 and a half to two hours. Season again before serving with pasta.