Cut tops from pineapples. With a sharp knife, hollow out fruit, leaving about 3/4 inch pineapple on sides and bottom. (Be careful not to cut through outside shells.) Dice 1 cup pineapple. (Use remainder for salad or dessert) Cook onions and garlic in cooking fat in large frying-pan 5 minutes, stirring occasionally. Add ground beef, salt, ginger, seasoned salt and pepper. Cook over medium heat, stirring occasionally, until ground beef begins to brown. Warm brandy in small pan over low heat, ignite and pour over beef mixture, lifting pan from heat and shaking until flame dies. Continue cooking for 8 to 10 minutes. Remove from heat; add 1 cup diced pineapple, orange segments and mandarine liquer, stirring carefully to mix. Fill pineapple shells (barrels) with beef and fruit mixture. Place filled fruit upright in foil lined pan. Bake in a moderate oven (350 degrees F.) for 35 minutes. Meanwhile remove stemms from mushrooms, slightly hollowing out caps. Cook caps in butter in small frying-pan about 3 minutes. Curl up each pimiento strip and place in mushroom cap. To serve, set both "Barrels" on warm plater, spoon beef mixture over rice on individual dinner plates and garnish each serving with 3 stuffed mushroom caps.