Core the tomatoes and cut a deep depression in the centre for stuffing. Above: Combine mushrooms and tomatoes to make an elegant starter â€” Mushrooms Lyonnaise. Squeeze the tomatoes gently to remove most of the seeds. Salt lightly, and turn upside down to drain. Meanwhile, combine the remaining ingredients in the container of an electric blender and blend on low or high speed until well pureed, or puree with a mortar and pestle. Spoon equal portions of the basil mixture into the centre of each tomato. Chill and serve cold.