along the breastbone line. Remove the fillets (the finger-size muscle on the back of each half) and reserve them for another use. Flatten each breast half with the flat end of a meat pounder until thin. 2. Heat the oil in a large skillet, add the breasts, and cook over medium heat until they are lightly colored, about 3 minutes per side. Remove from the skillet and set aside. 3. Add the shallots to the skillet and cook over low heat until they are translucent, about 5 minutes. 4. Add the vinegar, raise the heat, and cook, stirring occasionally, until it has reduced to a syrupy spoonful. Whisk in the stock, cream, and creme de casis, and simmer for 1 minute. 5. Return the breasts to the skillet and simmer them gently in the sauce until they are just done, about 5 minutes; do not overcook. 6. Remove the breasts with a slotted spoon. and arrange them on a heated serving platter. Simmer the sauce gently until it has reduced and thickened slightly, 3 minutes. Add the blackberries; cook 1 minute. Pour the sauce over the breasts and serve immediately, garnished with chervil leaves. Serves 4.