Preheat your oven to 200°C fan. Line a baking sheet with baking parchment.
Unroll your pastry sheet and lay in front of you with the longest side facing you. You can leave it on the greaseproof paper packaging to aid rolling.
Spread the cranberry sauce over the pastry sheet, up to the edges, leaving a 1cm gap along the longer top edge.
Sprinkle the bacon pieces evenly over the cranberry sauce, and then tear the brie into small chunks and dot over the bacon.
Use the pastry brush to moisten the 1cm gap with milk. Taking the closest, long edge to you, begin to roll up. Keep rolling until you have a ‘Swiss roll’ shape. With the seam-side down, cut into 16 equal shaped, spiral slices.
Arrange the slices onto the lined baking sheet, leave a small gap between each to allow them to puff up.
Brush the tops with a little milk then place in the middle of the oven for 15-20 minutes, until risen, crisp and golden brown. Serve.