Cook onions, leeks and shallots in butter wit salt and pepper, covered over med heat, stirring from time to time(10 minutes). Reduce heat and cont to cook over low heat for another 15 minutes. Remove cover continue to cook 3-5 minutes until excess moisture evaporates. Put onion mixture into 2 quart baking dish, stir in half and half, toss in bread crumbs and top with cheddar cheese. Dust with paprika. Bake at 375°F for 20-30 minutes