For the tomatoes with cheese filling, cut open the top of the tomatoes and remove the pulp with a spoon. For the filling, whisk together the cottage cheese, creme fraiche, onion, Worcestershire sauce and lemon juice until smooth. Crumble the cheese and fold in with the parsley. Season to taste with salt and pepper. Beat the egg whites until stiff and fold in. Fill the tomatoes with the cheese cream and serve with some parsley, if desired. Serve the tomatoes with cheese filling.