Slice firm tomatoes, keeping tops to use as lids. Clear out all seeds etc. and drain on a plate upside down.
Add a small amount of finely chopped onion, some browned bread crumbs, one beaten egg, a lot of dried parsley, salt and black pepper to the mince mixture.
Fill tomatoes with the mix, pressing well down. Place a small amount of butter on each. Put lids back on.
Place in an oven dish with 1 inch wall (border) and place in top of oven at gas mark 6 for 15–20 minutes.