Boil a kettle and pour enough hot water over your dried pasilla chilli to cover. Set aside to rehydrate for 15 minutes while you prepare the rest of the ingredients.
Place the flour in a large bowl and season well with sea salt and freshly ground black pepper.
Dredge the pieces of cubed lamb shoulder in the seasoned flour and set aside.
Heat 10 grams of the butter in a large saute pan and brown 1/4 of the meat on all sides. Transfer to a slow cooker. Repeat with the remaining meat.
Heat the remaining butter in the saute pan and add the onion, garlic and cumin seeds. Fry for five minutes or so until the onion begins to soften.
Add the tomato puree and lamb stock and stir well, scraping up any browned bits that might have stuck to the bottom of the pan. Add the tinned tomatoes and stir well.
Transfer the tomato mixture to the slow cooker and add the cinnamon sticks.
Drain and finely chop the rehydrated pasilla chilli, discarding the stem. Pop the lid on the slow cooker and set the timer on low for 6-8 hours.
15 minutes before you are ready to serve add the drained and washed borlotti beans and dark chocolate, broken into pieces, and allow it to melt into the chilli, stirring well.
Serve the chilli in bowls with a spoonful of soured cream, some sliced avocado and some mature cheddar cheese with some blue corn tortilla chips on the side.
Make your own lamb stock. It's cheaper to buy a whole lamb shoulder in the bone rather than ready cut cubed lamb. Carefully cut the lamb off the bone and use it in this lamb chilli recipe. Meanwhile, preheat your oven to 200C/400 F/gas mark 6. Arrange the bones with little bits of meat still stuck to them on a roasting tin. Halve two unpeeled onions (or quarter them, depending on the size), and add to the tin. Halve two carrots, lengthwise, and a few stalks of celery. Roast everything for 45 minutes. Transfer to a large stock pot, cover with cold water, bring to the boil and then skim. Reduce the heat and simmer with the lid on for 6-7 hours (or until your chilli is done). Strain and freeze the lamb stock in 300 ml batches for use in your next chilli recipe.