Remove top wing flat section from each wing. Place goose, breast-side up, in a baking dish or roasting tin.
Combine wing sections, water, wine and star anise in a saucepan and bring to a simmer over medium-high heat. Reduce heat to low and simmer until meat falls off the bone, about 2 hours. Remove bones and star anise; discard.
Preheat oven to 180 C / Gas 4.
Roast goose in the preheated oven until completely heated through, about 1 1/4 hours. An instant-read thermometer inserted into the thickest part of the thigh, near the bone should read 66 C (150 degrees F).
Stir balsamic vinegar, blackberry jam and black pepper into red wine mixture; simmer over medium heat until reduced by three quarters, about 15 minutes. Remove from heat. Whisk in cold butter until completely incorporated. Season with salt and pepper to taste.
Brush melted goose fat from bottom of roasting tin onto the goose breast. Drizzle with sauce and serve.