crackle crystals, to serve (optional) (available from specialist online retailers)
For the alginate bath, blend the bottled mineral water and algin powder in a food processor for 5-10 minutes, or until well combined.
Strain the mixture through a fine sieve, then pour the strained liquid into a large baking tray a least 5cm/2in deep. Chill in the fridge for 24 hours (this removes the air from the liquid).
Meanwhile, for the brioche, bring the cream, cinnamon, cloves and star anise to the boil in a pan. Remove from the heat and set aside to cool.
When the cream mixture has cooled, discard the cinnamon, cloves and star anise. Whisk the cream into the beaten egg. Add the sugar and whisk again until well combined. Submerge the brioche discs into the egg mixture to soak, then chill, covered, in the fridge overnight.
For the mango 'egg', add the gluco powder to the mango purée. Blend in a food processor until well combined, then transfer to a clean bowl. Cover and chill in the fridge overnight.
Using a small spoon or teaspoon, scoop four small portions of the chilled mango purée from the mixture and roll into balls, using your hands, or two teaspoons.
When all of the mango balls have been prepared, remove the alginate bath from the fridge. Carefully lower the balls of mango purée into the alginate mixture, leave for 30 seconds, or until a skin forms on the outside of the balls, then remove from the liquid using a slotted spoon and transfer to a bowl of water (this will rinse any remaining alginate off the egg).
Using an ice cream scoop or rounded dessert spoon, scoop four balls of Greek-style yoghurt. Carefully lower the balls into the alginate mixture.
Drain the 'yolks' from the water and return them to the alginate mixture, resting one on top of each ball of Greek-style yoghurt, in the centre to resemble a fried egg. Leave for 30 seconds, or until a skin forms on the 'egg'.
Remove from the alginate mixture using a slotted spoon and transfer to a fresh bowl of clean water (this will rinse any remaining alginate off the egg).
When ready to eat, heat the vegetable oil in a non-stick frying pan over a medium heat. Add the soaked brioche discs to the pan and fry for 2-3 minutes on each side, or until golden-brown on both sides. Add the butter and icing sugar to the pan and continue to cook the brioche until the butter has melted, the icing sugar has dissolved and the brioche discs are caramelised.
To serve, paint a smear of mango purée across the centre of each of four serving plates. Place one brioche disc into the centre of each plate. Place a mango 'egg' on top of each brioche disc. Garnish with a sprinkling of crackle crystals, if using.