Sprinkle the skinned chicken pieces with salt and pepper, then dredge in the flour. Melt the butter with
the olive oil in a heavy skillet on medium heat and gradually add the chicken pieces. Brown the chicken on all sides and remove from the skillet.
When all the chicken has been browned, add the onions and garlic to the skillet and cook on medium heat, stirring occasionally for five minutes. Add the white wine and scrape any bits clinging to the bottom and sides of the skillet into the wine. Add the tomatoes, bouillon cube, and dried thyme, then the browned chicken pieces. Cover the skillet and simmer on low heat for 30 minutes.
Add the mushrooms and continue cooking for 15 minutes. Stir in the cognac 5 minutes before the end of the cooking time. Stir in the chopped herb just before serving.