Place a large pan over medium heat and add oil, butter and onion to it. Cook until onion becomes transluscent, stirring constantly. Add celery and continue cooking for two more minutes.
Add ground beef and season with salt and pepper. Cook until beef is no longer red, breaking up the clumps with a spatula.
Pour in heavy cream and bring to a simmer. Stirring often, keep simmering until almost all cream evaporates.
Add nutmeg and stir to combine with the rest of the sauce.
Pour in white wine and do the same thing we did with the cream - simmer and stir, until it evaporates.
Time to add our tomatoes! Pour them in and stir well.
Bring the sauce to a simmer and turn the heat to low. Continue to cook for up till 3 more hours, tasting time to time. While real Bolognese sauce takes 4 full hours to cook, you may remove the sauce from the heat sooner, if you find that it's done to your liking.
Troubleshooting tip: if your sauce begins to dry out before 3 hours have passed, feel free to add a little water, to keep it from sticking. Just make sure it's all evaporated before you remove the finished product from the stove.
Serve on top of zucchini noodles, garnished with freshly grated parmigiano-reggiano.