On a cutting board cut the chicken breast lengthwise to form 2 equal size fillets.
Cut up the onion/shallot and set aside.
Melt butter into 12inch skillet. Raise the heat to medium add the chicken breast fillets cook for about 3 minutes per side. Remove from skillet and set aside.
Add onion to the fat in the pan and cook covered over low heat until tender about 10 minutes.
Add the vinegar, raise the heat and cook, uncovered, stirring occasionally, until vinegar is reduced to a syrupy spoonful.
Wisk in the chicken stock, heavy cream and crushed tomatoes and simmer for 1 minute.
Add chicken fillets to the skillet and simmer them gently in the sauce basting them often, until they are just done and the sauce has been reduced and thickened slightly, approximately 4-5 minutes; Do not overcook.
Remove chicken fillets with a slotted spoon and arrange on a heated serving tray. Add the raspberries to the sauce in the skillet and cook over low heat for 1 minute. Do not stir the berries with a spoon, merely swirl them in the sauce by shaking the skillet.
place the chicken fillets on a plate and pour raspberry sauce with cooked raspberries over chicken and serve. Enjoy!
