In a large bowl, mix the chicken with onion, garlic, a-tablespoon oil, angelica, allspice, salt and pepper. Leave in the fridge to marinate for at 7-8 hours.
Heat the butter and a-tablespoon oil in a pot over medium-high heat until hot. Add the chicken and saute until no longer pink (about 3-4 minutes), stirring occasionally.
Add the mushroom and saute for 2-3 minutes.
Dissolve the saffron in the warm milk and add to the stew. Cover the pot and simmer over medium heat for 15 minutes, stirring occasionally.
Then mix the sour cream, heavy cream and oregano. Add to the stew. Cover the pot and simmer over medium-low heat until the stew is thickened (about 2 hours), stirring occasionally (it is ok if chicken starts to fall apart). Add more milk if needed. Taste and adjust seasonings.
Serve with rice or bread.