In a small pot, bring the chicken stock, Worcestershire sauce, and half and half to almost a simmer. Keep the heat low to prevent simmering.
In a large dutch oven or oven-safe pot, melt the butter over medium heat. Cook the carrots, celery, and onion until the onions become translucent. Add in the parsnips and garlic and cook until the garlic becomes fragrant.
Melt the second half of the butter and and then stir in the flour until all of the vegetables are well coated. Cook for 1-2 minutes. Slowly stir in the hot liquid from the small pot, stirring constantly until combined. Add the frozen peas, thyme, bay leaf and shredded turkey. Let simmer for 20 minutes.
Preheat the oven to 400°F
In a medium bowl, whisk together the flour, baking powder, baking soda, rosemary, and salt. In a measuring cup, whisk together the egg and buttermilk.
Make a well in the center of the flour mixture and pour the liquid into the center. Use a fork to mix together the ingredients, being careful to move it as little as possible so it doesn't over-mix and become tough.
Remove the turkey stew from the heat and use a spoon to drop the rosemary dumpling dough onto the top. Cover with a lid and bake in the preheated oven for 20 minutes, or until the dumplings are cooked through.
Remove from the oven and allow to rest for 10 minutes for ultimate thickening.
Make sure to use a dutch oven or pot that is safe to go into the oven. Not all pots are designed to go up to 400°, so double check if you aren't sure.
Remember that cooking times will vary depending on how shallow your dutch oven or pot is.
Because the dumplings are cooked on top of the simmering liquid instead of in it, they won't "float" when they are done.