Put the onion, carrots, celery and beef in a large non-stick saucepan and dry-fry over a high heat for 2-3 mintes, until the beef is no longer pink. Keep stirring with a couple of wooden spoons to break up the mince.
Reduce the heat and add the ketchup, brown sauce, Worchester sauce, flour, chilli powder and chilli flakes [if using] and blackpepper.
Cook for a minute, then add potatoes and stock.
Bring to he boil, reduce the heat and cover loosely. Simmer for 25 minutes until potatoes are tender, stirring occasionally.
Remove from heat, stir in frozen peas and leave to cool [if using for pies]/serve.