Preparation In a large heavy skillet heat 4 tablespoons butter over moderate heat until foam subsides and cook herbs 3 minutes. Add onion and cook over moderately low heat, stirring occasionally, 30 minutes, or until softened. Add mushrooms, dill, remaining 4 tablespoons butter, and salt and pepper to taste and cook, stirring occasionally, 15 minutes, or until mushrooms are tender. In a bowl stir together eggs, sour cream, and matzo and let mixture stand. Preheat oven to 375° F. and butter a 13-by-9 inch baking dish. Under running water, coarsely grate potatoes into a colander. Squeeze excess water from potatoes and drain 2 minutes. Stir potatoes and onion mixture into matzo meal mixture. Spoon mixture into dish and bake in middle of oven 50 minutes, or until golden. Potato kugel may be made 1 day ahead, and chilled, covered.
Preparation In a large heavy skillet heat 4 tablespoons butter over moderate heat until foam subsides and cook herbs 3 minutes. Add onion and cook over moderately low heat, stirring occasionally, 30 minutes, or until softened. Add mushrooms, dill, remaining 4 tablespoons butter, and salt and pepper to taste and cook, stirring occasionally, 15 minutes, or until mushrooms are tender. In a bowl stir together eggs, sour cream, and matzo and let mixture stand. Preheat oven to 375° F. and butter a 13-by-9 inch baking dish. Under running water, coarsely grate potatoes into a colander. Squeeze excess water from potatoes and drain 2 minutes. Stir potatoes and onion mixture into matzo meal mixture. Spoon mixture into dish and bake in middle of oven 50 minutes, or until golden. Potato kugel may be made 1 day ahead, and chilled, covered.