Rinse and drain lentils and rice. Place together in a medium-sized saucepan with 2 cups water. Bring to a boil. Reduce heat and simmer covered until water is absorbed and lentils and rice are cooked (about 45 minutes).
Meanwhile, in a large skillet, gently heat butter or margarine, vegetable oil, garlic, allspice, and salt. Stir in onions and sauté until soft.
Combine lentil and onion mixtures. Run the mixture through a food mill or process with the steel blade of a food processor until puréed. Serve hot or cold on crackers or bread
Note: To serve a molded hors d’oeuvre, pack the pâté into a lightly greased mold or small loaf pan. Chill well. Unmold, place on a serving platter and surround with crisp crackers.