1–2 large leeks, thickly sliced
1 tsp English mustard powder
500–600ml/18–20fl oz chicken stock
325g/11½oz pasta shapes, like farfalle or penne
50²µ/1¾´Ç³ú plain flour
salt and freshly ground black pepper
50²µ/1¾´Ç³ú butter
150g/5½oz mature cheddar, grated
500ml/18fl oz milk
2 tbsp grated Parmesan
6–8 rashers streaky bacon, cut into 2cm/¾in strips
500g/1lb 2oz leftover cooked chicken or chicken breasts, skin removed