Bring a large pot of lightly salted water to the boil. Add the shallots, and cook uncovered for 3 minutes until just tender. Drain in a colander, then immediately immerse in ice water, or rinse with cold water for several minutes until cold to stop the cooking process. Once the shallots are cold, drain well, and set aside.
Heat the olive oil and butter in a casserole or large pot over medium heat until oil is hot and butter is melted and bubbling. Add the whole, blanched shallots and chicken pieces to the pot and cook, turning chicken pieces over until no longer pink inside and shallots have softened and turned translucent, about 15 minutes. Stir in the chopped garlic and cook for another 3 minutes, until garlic starts to turn golden.
Pour in red wine and passata, and add the parsley, salt, pepper, oregano and bay leaves. Pour the chicken stock over the chicken pieces to cover, and stir to combine.
Simmer the stew, covered, over medium-low heat for about 50 minutes, until the shallots are soft and the chicken is tender.
Absolutely delicious and extremely simple. Was richer than I thought it would be. Adjustments I made, no shallots available here in Spain so used onion and extra garlic. Served with Greek potatoes (Recipe by Nicola on this site) which were fab, together with simple oven baked asparagus and Tina's Greek Stuffed Peppers with Feta Cheese (also on this site. Overall a lovely delicious meal. - 12 Nov 2012