Heat a large frying pan on a medium heat and add peppercorns, cumin seeds, coriander seeds and roughly chopped dried chillies Toast them for a minute or two or until you have a fragrant smell of spices.
Add the toasted spices to a coffee grinder and grind until they are like a fine powder. Transfer to a mortar and pestle, add crushed garlic cloves, ginger, turmeric and use the pestle to combine.
Next add 1 tbsp olive oil, apple cider vinegar, cinnamon to the mortar and use the pestle again until you have combined ingredients to make a paste.
Add 2 tbsp oil to the frying and heat on a medium high. Add in the onion, fry for a couple of minutes, then add in the chilli and fry for another minute. Add in the beef and brown the meat. Once browned add in the paste and cook for a couple of minutes, then transfer to the slow cooker.
Add in the tinned tomatoes and cook on high for 3- 4 hours or 6-8 hours on low.