Steam or boil the broccoli until tender but still crisp.
Fry mushrooms in oil and butter over medium heat. Add leek and garlic. Once soft, remove from heat. Combine with the mashed butter beans, crumbled Stilton and beaten egg.
Chop the cooked broccoli and add it to the mixture.
For the pastry: Boil water and margarine. Remove from heat. Add the flour all at once and mix well. Allow mix to cool so that it can be handled, then knead. Roll out half and line a 18 or 20 cm shallow pie dish. Roll out the other half for the top.
Add filling, roll out pie top and bake for 20 minutes at 220 degrees C for 20 minutes, then reduce heat to 190 degrees C for a further 40 minutes.