Mushroom and Dumplings

Name: Mushroom and Dumplings
Ingredients: 4 tablespoons unsalted butter (2 ounces; 56 g), divided; 1 1/2 pounds (680 g) cremini, button, or portobello mushrooms, stemmed and cut into 1/4-inch thick slices; 2 medium leeks (about 1 pound; 454 g), light green parts only, finely chopped; 3 medium ribs celery (5 ounces; 141 g), finely chopped; 2 medium cloves garlic (10 g), minced; 1 teaspoon minced fresh thyme; 1 1/2 tablespoons (12 g) all purpose flour; 5 cups (1.2 L) homemade or store-bought low-sodium mushroom, vegetable, chicken, or beef broth, plus more as needed; 1/2 ounce (14 g) dried porcini, morel, chanterelle, lobster, or shiitake mushrooms; 2 teaspoons (10 ml) light soy sauce; Freshly ground black pepper; 1/3 cup (80 ml) heavy cream; 1 teaspoon fresh lemon juice, plus more to taste; 1 1/2 cups all-purpose flour (6 3/4 ounces; 192 g); 1 1/4 teaspoons Diamond Crystal kosher salt; for table salt, use half as much by volume; 1 teaspoon baking powder; 1/2 teaspoon baking soda; 3 tablespoons finely chopped flat-leaf parsley; 2/3 cup (160 ml) buttermilk; 1 large egg; 3 tablespoons unsalted butter (1 1/2 ounces; 42 g), melted and slightly cooled