Mix the ginger, syrup and honey in a bowl, then add the plum halves and stir to coat.
Cut 4 x 45cm lengths of foil and fold each one in half to make a double layer. Place a square of baking paper in the middle of each one.
Divide the plums among the squares and bring the edges together to seal and make a parcel. Place on the barbecue rack over glowing coals and cook for 10-12 minutes, until the plums have softened slightly.
Carefully open the parcels, discard the foil, top with the granola and serve with ice cream, if you like.