10 ounces cremini mushrooms, diced 3 tablespoons butter 1 teaspoon salt 3 green onions, sliced 1 teaspoon black pepper For the dumplings and assembly 4 cups peeled potatoes, about 1 teaspoon salt 1 egg, lightly beaten 3/4-inch dice 1/2 teaspoon white pepper 1 1/2 to 2 cups all-purpose flour Melted butter for drizzling or browning For the filling: Sauté the mushrooms, green onion,