Hold the Brie cheese flat with the palm of your hands and split horizontally. Brush with the cranberry sauce and sandwich back together, cut into 6 wedges. Roll the puff pastry into a long strip, double the width of the cheese bites. Brush with the mustard and put the Brie on top, fold over the pastry and press the edges to secure the edges. Push an ice cream stick into the thick part of the wedges and chill, allowing pastry to rest. Brush with beaten egg and sprinkle with poppy seeds. Bake in a hot oven until pastry is golden and crispy.