Mix together the mayonnaise and curry powder. Tear the chicken into thin strips with your fingers and cut up the peaches – you can do this up to 2 days before. Keep in the fridge until needed. To serve, spoon some of the mayonnaise mixture over the crostini, lay chicken pieces on top and finish with a couple of peach slices.
For the crostini bases, cut each of the 4 baguettes into 20 slices, ½cm thick, discarding ends. Drizzle with olive oil and place under the grill. Cook for 2-3 mins until lightly golden, then turn over and cook for another 1-2 mins until golden and crisp all over. Do this in batches and store in a large, airtight container at room temperature for up to 3 days.