Heat large saucepan over medium-high heat, add oil and swirl to coat. Place chicken in pan and cook 5-6 minutes per side. Chicken will not be cooked through, but skin will be lightly golden. Remove chicken, and set aside.
Discard all but 1 tablespoon of fat from pan. Return to heat and reduce to medium. Add prosciutto and onions. Cook 2-3 minutes, until onions start to get translucent. Stir in leeks and continue cooking for another 2-3 minutes or until leeks start to soften.
Add celery root, sweet potato, rosemary, tarragon and salt. Stir to mix. Cook, stirring occasionally, until root vegetables start to soften, about 5-6 minutes.
Return chicken to pan and add broth and lemon juice. Turn heat up to high and bring to a boil, then reduce heat to medium-low, cover and simmer for 25 minutes.
For the dumplings
In a small bowl combine flour with baking powder, baking soda, salt, chives, parsley, rosemary, onion powder and black pepper. Stir in water and lemon juice until smooth. Set aside.
Remove chicken from pan. Continue simmering vegetable mixture, uncovered for 5 minutes.
Using 2 forks, remove skin and shred chicken. Discard bones and skin.
In a small bowl, mix cornstarch with 1/4 cup (60 mL) of hot broth from vegetable mixture. Stir into sauce until thickened. Return shredded chicken to pan.
Drop dumpling dough by the tablespoon into stew. (you’ll have 10-12 dumplings). Spoon sauce over dumplings. Cover pan and simmer for 10-15 minutes or until dumplings are doubled in size and cooked through.
Season stew with black pepper to taste. Serve it in bowls, topped with 2-3 dumplings on top, and garnish with chives.
*For chickpea flour, look for allergy-friendly, gluten-free brands. To make your own, place dried chickpeas in a high-speed blender or food processor, and pulse repeatedly, until flour consistency is reached.