Heat the broth in a large wide-mouthed (critical for all the dumplings) pot or dutch oven over high heat until it comes to a simmer. Add the chicken to the simmering broth and let it return to a simmer.

Cover the pot, reduce the heat to medium low, and continue simmering another 8-10 minutes until the chicken is just cooked.

Transfer the chicken to a plate, tent it with aluminum foil, and let it rest while you prepare the rest of the stew. Strain the chicken broth into a large bowl and wipe out the pot.

Melt the butter in the empty pot over medium heat. Add the onion and salt, saute for 5-7 minutes, until soft. Add the mushrooms, continue sauteing 10-15 minutes until browned. Stir the minced garlic into the onions and mushrooms, cook another 30 seconds until garlic becomes fragrant.

Add in the flour and cook 1 minute, stirring frequently, until toasted but not burnt. Quickly add the sherry, scraping up any browned pieces in the pan. Add the reserved broth, milk, cream, thyme, bay leaves, and pepper. Turn the heat up to high and bring the mixture to a boil. Cover, reduce the heat to low, and gently simmer about 20 minutes until the stew thickens.

Meanwhile, whisk together the flour, baking powder, and salt in a large bowl. Make a well in the center and stir in the buttermilk to form a shaggy, thick dough.

Shred the poached chicken into bite-sized pieces. Remove the bay leaves from the soup and turn up heat slightly to obtain a rapid simmer. Add the shredded chicken, any accumulated juices, the frozen peas, and 3 tablespoons of the minced parsley into the stew and stir.

Use two large soup spoons or an ice cream scoop with a lever to place golf-ball sized rounds of the dumpling dough onto the stew, about ¼ inch apart. You should end up with 16-18 dumplings dotted over the surface (this is why you need a wide-mouthed pot).

Drop the heat back down to low, cover, and continue cooking another 15-18 minutes until dumplings have doubled in size.

Garnish the stew with the remaining tablespoon of parsley and serve.