Chop your onion, sausages, and mushrooms and place in a pan with some oil. Put potatoes on to boil (boil them until they are ready to be mashed).
Step 2:
when sausages are cooked, add your gravy and tomato puree and stir together.
Step 3:
add pepper, salt, some garlic and red wine for taste.
Step 4:
cook it all until the potatoes are ready to be mashed. Mash them, and put the mixture into a casserole dish. Put mashed potato on top, and pop in the oven for a few minutes to keep warm.