1. Pour olive oil into a multi-functional pressure cooker (such as an Instant Pot) and select the Sauté function. Cook and stir onion, carrot, celery, and bay leaf until vegetables are soft and onion has turned translucent, about 5 minutes.

2. Add chicken broth, thighs, breasts, salt, thyme, marjoram, and black pepper. Close and lock the lid. Select high pressure according to manufacturer's instructions; set the timer for 9 minutes. Allow 10 to 15 minutes for pressure to build.

3. Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Carefully use tongs to remove chicken pieces to a large bowl to cool slightly; discard bay leaf.

4. While chicken is cooling, mash butter with flour in a small bowl to make a smooth paste; set aside.

5. Make dumplings: Combine flour, baking powder, and salt in a medium bowl. Cut in cold butter with 2 knives or a pastry blender until mixture resembles the texture of cornmeal. Stir in parsley and set aside.

6. Shred cooled chicken and return to the pot. Taste broth and season with salt and pepper if needed. Add peas and green beans. Stir in flour-butter paste until incorporated. Select Sauté function and bring broth to a boil.

7. Pour buttermilk into dumpling mixture and stir until combined. Drop dough by heaping spoonfuls over the top of stew.

8. Close the lid, leaving the steam vent open. Select Slow Cooker function and simmer on Low, covered, until a skewer inserted into the center of a dumpling comes out clean, 10 to 12 minutes.

Tips

You can use a mini food processor to cut in cold butter in step 5. Transfer the flour-butter mixture to a medium bowl before adding buttermilk.

You can use a small cookie scoop to drop dumpling dough over stew.

To use this as a pot pie filling, decrease chicken broth to 2 cups.