Pre-heat the oven to 200°C.
On a lightly floured surface, roll the pastry out into a large square with a thickness of 1cm. Cut into individual squares measuring 10cm x 10cm. Transfer to a lined baking sheet, prick a few times chill in the fridge.
Prepare the caramel by mixing the sugar and water in a wide heavy-based frying pan. Dissolve the sugar and water over a medium heat and once it the sugar has dissolved, increase the heat and let the caramel cook and bubble for a further 4-5 minutes. Remove from the heat and add the cream and butter, swirling to incorporate. Add the segmented mandarines and clementines and swirl to cover.
Bake the pastry for 12-15 minutes until golden and risen.
Meanwhile prepare the garnish by dipping the cherries in the lightly beaten egg white and rolling in the 25g of caster sugar. Shake off any excess and chill in the freezer until serving point.
Remove the pastry and gently warm the caramel to loosen if hardened. Cut squares out from the middle of the pastry, leaving a 2 cm border all around. Spoon the mandarin caramel mixture inside and arrange on a serving plate. Garnish with the frosted cherries and sprigs of mint.