Method
1. In a small saucepan, combine the cranberry sauce, vinegar, red onion and 1/4 cup of water over medium heat. Season with salt and pepper and cook until onions are tender, and sauce has slightly reduced. Take off heat then set aside to cool.
2. Preheat the oven to 180°C.
3. Lay the pastry on a tray on baking paper. Cut the edges of the square pastry to make a rough circle then mark a circle with a smaller plate or bowl to make an inner circle. Make 4 cuts in the inner circle, like you are marking an asterisk.
4. Spread the cranberry onion jam around the outer circle leaving a 1-2cm border around the outside, then arrange the slices of brie and rosemary sprigs on top.
5. Take one point of the centre star over the filling as well as bringing the outer edge of pastry inwards. Press the two together and continue until you have a wreath.
6. Brush the tops of the wreath with egg then place in the oven for 15-20 minutes or until puffed and golden brown.