Bring meat to room temperature and add plenty of salt.
In the cast iron pot, on medium heat add oil and sear and brown the meat in batches so you don't over crowd the pan. Do this until all the sides of the meat are browned to your taste
In the other pot add the chillies, onion, garlic, tomatoes and whole spices. Cover with water, cover and leave on high heat for about 30 minutes.
Once the chillies and tomatoes are very soft drain everything in a colander saving 1 cup of the liquid.
Allow to cool a little before adding everything to a blender. Along with 1 cup of the liquid it cooked in. Blend until completely smooth.
Once the sauce base is ready add the beef back to your cocotte on medium heat and pour the blended sauce on top.
Pour 800ml of beef stock into the blender cup to collect all the remaining sauce from the sides and add to the pot. Bring it to a gentle simmer and then cover and put in a preheated oven at 150°C/200°F .
Leave to braise for 3-4 hours. I left mine for 4 hours for super tender meat.
When done collect the fat/oil on the top of the sauce with a spoon into a separate bowl for ease.