Using a food processor, blitz two carrots, three stalks of celery, the garlic, and the onion until finely chopped. You can blitz them together or separately depending on the capacity of your food processor. Set aside.
Cut the remaining carrot and celery into chunky pieces. Set aside.
Heat a pan over medium heat and add a little oil. Gently sear the bacon until browned and the fat has rendered.
Add the beef shin and cook until nicely browned on all sides.
Add the blitzed vegetables and stir to combine.
Pour in the red wine, bring to a boil, and let everything simmer on low heat for about 45 minutes.
Add the vegetable chunks, canned demi-glace sauce, Worcestershire sauce, and vegetable stock.
Let it simmer for another hour until the sauce is thick and rich.
Finish with dark chocolate and stir until melted.
If preparing ahead, reheat gently before serving.