Rinse your carrots, peel them, and trim off the ends. Dice the carrots. Rinse your celery, scrub off any dirt, and dice the celery.
Peel and chop your garlic finely.
Melt your butter with the oil in a large sauce pot over medium-high heat. Add the onion, carrots, celery and garlic and stir to combine. Cook this "soffritto" until tender.
Stir in your ground beef and sausage, breaking up the meat with a wooden spoon. Cook over medium heat, stirring occasionally, until the meat is no longer pink. (If you see lots of liquid, you can drain some. Leave some for flavor.)
Stir in your wine (use a clean spoon) and let it come to a boil. Reduce the heat and simmer for five minutes, until the wine is evaporated.
Stir in your tomato paste, beef stock and half and half. Heat until boiling, then reduce the heat to a simmer. Cover the pot, propping your lid open by leaving a wooden spoon resting on the edges of the pot.
Simmer 45 minutes, stirring occasionally. (Start preparing your pasta when there are about 15 minutes left.)
Tightly roll up a couple basil leaves at a time into a long cylinder. Use kitchen scissors or a small knife to cut them into thin ribbons. Stir the basil into your sauce when it's done (save some to garnish each serving, if you wish.) Taste your Bolognese to see if any salt and pepper are needed. See notes.)
Drain your pasta when it's al dente and return it to your pot. Stir in two or three ladles of Bolognese sauce, so the pasta isn't dry.
Serve the spaghetti topped with more Bolognese, along with grated Parmesan and basil ribbons, if desired.
Store leftover sauce and pasta separately in the refrigerator for up to five days.
The recipe as written doesn't have salt or pepper added, due to the seasonings in the hot Italian sausage. If you decide to skip the sausage, you will have to add salt and pepper. This makes enough sauce for at least 8 servings, but I usually cook one pound of pasta with it and save the extra sauce. For a low-carb option, serve the Bolognese over cooked spaghetti squash or zucchini noodles.