Discard the muddy bottom of the mushrooms and wash under running water. Wipe with a cloth, halve or quarter the large mushrooms. Skin, seed and dice the tomatoes. Heat 2 tablespoons olive oil in a small high-sided frying pan, pour in the tomatoes, cook uncovered with the bouquet garni for 5 to 6 minutes. Add the mushrooms, juice of 1 lime, green peppercorns and salt. Cover and cook over a medium heat for about 20 minutes. Remove from the heat (or take out of the oven), uncover, add the rum, juice of the second lime, tomato ketchup and 1 tablespoon olive oil. Combine and chill in the refrigerator.
