Broil chicken thighs, skin-side up, 4 to 6 inches from heat for 8 to 10 minutes until deeply browned. Set aside with any rendered fat.
Cook onion, carrot, and celery in butter for 6 to 8 minutes until softened.
Stir in garlic for 30 seconds.
Sprinkle in flour and cook 1 to 2 minutes to form a roux.
Gradually whisk in chicken stock.
Add potatoes, thyme, bay leaf, and broiled chicken with its fat. Simmer covered 30 to 35 minutes until tender.
Remove chicken, pull into large pieces discarding bones, and return to the pot.
Stir in peas, warm 3 to 5 minutes. Season, remove bay leaf, and garnish with parsley.