How to Make It
Melt butter in an Instant Pot set to sauté. Add celery, carrots, onion, and garlic; cook until soft and fragrant, 5 to 8 minutes. Sprinkle 2 tablespoons flour over vegetables, stir, and cook 1 minute.
Add 7 cups water, bouillon, turkey, 1 tablespoon sage, bay leaves, and 1/8 teaspoon pepper. Cover and cook on high pressure 20 minutes. Release pressure with quick or natural release. Remove turkey; shred or chop. Discard bay leaves; return turkey to pot. Turn Instant Pot to sauté; bring back to a boil.
Combine remaining 1 cup flour, baking powder, remaining 1 teaspoon sage, salt, and remaining 1/8 teaspoon pepper. Whisk together egg yolk and milk; stir into flour mixture until just blended. Form dough into dumplings using a teaspoon, and drop into soup. (They will expand.) Partially cover; cook until dumplings are cooked through and tender, about 3 minutes. Garnish with pepper and parsley.