3–4 medium carrots, about 300g/10½oz, peeled and cut into 1.5cm/½in chunks
1 celery stick, trimmed and thinly sliced (optional)
1 medium onion, finely chopped
1.2kg/2Ib 10oz potatoes, ideally Maris Piper, peeled and cut into 3–4cm/1½in chunks
1 tbsp plain flour
3 tbsp Worcestershire sauce
salt and freshly ground black pepper
1 tsp dried mixed herbs
3 tbsp tomato purée
75²µ/2â…”o³ú butter, cubed
100ml/3½fl oz milk
500g/1lb 2oz lamb mince
275ml/9½fl oz hot lamb stock, made with 1 stock cube