Preheat the oven to 170°C / 325°F
Place ½ tablespoon of the oil in a skillet and heat over a medium to high heat.
Place the chicken breasts in the skillet and sear for a couple of minutes before flipping over to sear the other side. You are not cooking the chicken through at this stage - you will do this in the oven later. The purpose is to brown the chicken slightly so that when it is baked in the oven later it retains it moisture and is juicy and succulent!
Remove the chicken breasts from the skillet and place in an oven proof dish. Cover with kitchen foil and set aside.
Using the skillet that you used to cook the chicken, add the remains of the oil and then add the chopped onions.
Cook the onions over a medium heat, stirring often, until they have softened and have started to brown.
Once the onions have begun to brown and are nice and soft add the can of ginger beer, the Worcestershire sauce and a little salt and pepper.
Bring the sauce to a boil then reduce the heat to a simmer and cook for approx 15 minutes or until the sauce has reduced by ⅓ or so. You want the sauce to have started to thicken slightly and darken in colour a little.
Remove from the heat, remove the kitchen foil from the chicken and pour the sauce over the chicken breasts,
Place in the centre of your preheated oven.
Bake for 35 to 45 minutes until the sauce has thickened and the chicken is cooked through (use a meat thermometer to check this - the internal temperature needs to be 165°F).
Serve, enjoy and track!