Place chicken and garlic in large pot, cover with water and bring to boil.
Cook thighs until done. Remove from heat and let steep in cooking liquid until roux is ready.
Remove chicken from pot, dice chicken. Skim off fat and reserve stock.
Roux
Melt butter.
Add onions and garlic and sweat until tender.
Add flour to form a roux. Do not brown the flour.
Assemble
Add half the broth to roux to form veloute.
Bring up to temperature.
Add cooked, diced chicken and sour cream.
Adjust consistency with remaining stock.
Season to taste with salt and white pepper.
Serve with cooked rice, garnish with parsley.