Cream butter with sugar until light and fluffy. Gradually beat in one egg yolk at a time until thoroughly blended. Stir in melted chocolate along with rum or coffee; add almonds and crumbs. Fold in stiffly beaten egg whites gently but thoroughly, using a rubber spatula. Butter a melon mold and sprinkle inside with sugar, tapping out excess. Turn filling into mold, which should be about two-thirds full. Cover and set in water bath that comes two-thirds up the sides of the mold. Steam 1 to 1½ hours, or until pudding is completely set, and let stand for a few minutes after it is done. Uncover and invert onto serving platter.