Peel and chop the potatoes, and place into a pot to boil with a pinch of salt.
Brown the mince in a pan, adding the Worcestershire sauce and the stock cube. Add the mushrooms and finely chopped onion and stir through and cook for 5-7 minutes
Place the cooked mince mixture in the bottom of a large casserole dish, and add the baked beans and tomatoes. Turn on oven oven to 200 degrees C and leave the casserole to warm through while the potatoes finish cooking.
Once your potatoes are finished, drain and mash them, adding the butter and milk to make a creamy mix. Remove the casserole dish from the oven and sprinkle the mince mix with the gravy mix stirring until the mixture becomes thick.
Very carefully dollop the potato in blobs over the top of the thickened mix and gently spread it out to make a pie top, rake it over with a fork and place back in the oven.
Cook for 10 minutes or until the topping is golden and crispy.