Preheat the oven to 200ºC, gas mark 6.
Heat 10g of the butter in a large saucepan and gently fry the onions for 15 minutes covered, until softened and golden. Add 2 tbsp flour and cook for 1 minute. Stir in the Worcestershire sauce and stock and bring to the boil stirring. Transfer to a casserole dish and bake for 20 minutes.
Meanwhile, rub the remaining butter into the 225g flour to form breadcrumbs. Stir in the cheese and seasoning and stir in enough of the milk to form a dough. Knead slightly on a floured surface then roll out to 1.5cm thick and cut 8 circles using a 7cm round cutter.
Place on top of the soup and bake for a further 15 minutes until cooked.
Try adding a dash of white wine with the stock to give an extra rich flavour.
Freezing and defrosting guidelines
Make the soup, then leave to cool at room temperature. Freeze (without garnishes or toppings) in a rigid container, leaving a bit of space for expansion, for up to 1-3 months. Reheat either from frozen or defrost in the fridge overnight. Once piping hot, add toppings or garnishes and serve.