Season meat with salt & pepper and sear in pan with beef fat (or oil) until browned on all sides, then remove
Deglaze pan with mustard, tomato purée, balsamic, soy sauce & Worcestershire sauce mixed together
Chop baby potatoes in half and add to slow cooker along with mixture you've just deglazed the pan with and the browned beef brisket
In the deglazed pan: melt knob of butter, add fresh rosemary, mixed herbs, celery, carrot & onion and allow to soften before adding garlic to cook for 1 minute
Then pour in the red wine, allow volume to reduce by half, stir through flour to help thicken the sauce and add it all into slow cooker
Finally, add bay leaves & beef stock - cook for 8-10 hours on Low
Remove the lid, skim the fat off the top and remove the bay leaves then lift the beef brisket out to shred
Add frozen peas and shredded beef back into slow cooker & cook for a further 30mins on High with lid off before serving
