In a large skillet, saute mushrooms in batches in 1/4 cup butter until mushrooms are tender and liquid is evaporated. In a large bowl, whisk the cream, egg yolk, parsley, lemon juice, salt and paprika. Add mushrooms and stir until blended., Transfer to a greased 8-inch square baking dish. Melt remaining butter; stir in cracker crumbs until blended. Sprinkle over mushroom mixture. Cover and refrigerate overnight., Remove from the refrigerator 30 minutes before baking. Preheat oven to 350°. Bake, uncovered, until a thermometer reads 160° and topping is golden brown, 30-35 minutes.