Heat the oil in a large stock pot over a medium heat
Add the bacon, onion, celery and carrots and mix well with the oil. Reduce heat to a low medium, add a pinch of salt and cover for 6-8 minutes, stirring occasionally, until vegetables have softened.
Stir in the garlic and cook for another 2-3 minutes stirring occasionally
Turn heat up to medium high and add browned mince. Mix well and cook for 4-5 minutes stirring often.
Add flour and tomato puree and cook for 3-4 minutes, stirring constantly to cook out the rawness of these two ingredients
Add wine and scrape the bottom of the pan vigorously then add the stock and tomatoes and stir frequently until the mixture begins to simmer
Turn down to a low heat until the mixture is just slowly bubbling then add oregano, nutmeg and a pinch of salt and pepper. Mix well
Drop in the parmesan rind at this point if using and remove it at the end of the cooking time. The rind will impart its flavour into the dish adding another subtle layer of flavour
Partly cover with a lid and cook for at least 1 hour, maybe 90 minutes depending on the finished consistency you want, stirring the mixture frequently and making sure it doesn't stick to the bottom of the pan during this cooking period
15 minutes from the end of the cooking time, taste and add any more of the herbs, spice or salt and pepper you think you need. You may also wish to add a tablespoon or two of sugar depending on the red wine you've used. Balance the dish and adjust the recipe to your own preference. At this point, also add the grated dark chocolate if using. This will add a richness and depth to the finished bolognese
At this point add your spaghetti to a deep pan of salted boiling water and cook until almost soft but definitely not soggy
Drain the pasta and add to your sauce, stirring well for a couple of minutes. Alternatively (especially if you've made extra sauce) put the pasta back in the dry pan on a very low heat and add the amount of bolognese sauce you wish. Stir for a couple of minutes until beautifully combined