Spread one slice of brioche with a generous layer of hazelnut creme. Top with another slice of brioche (to create a sandwich) and spread generously with the remaining hazelnut creme. Top with the final slice of brioche to make a big three-tiered brioche sandwich. Remove the crusts and set aside.
In a wide, shallow bowl, whisk the eggs, milk and vanilla extract to combine. Dip the brioche sandwich into the egg mixture, turning to coat both sides. Take care not to submerge it for too long or it will go soggy.
Heat a knob of butter in a medium-sized non-stick frying pan and set over a medium heat. Once the butter is foaming, swirl to coat the base of the pan, then add the brioche sandwich.
Fry for about 1 minute - or until golden brown underneath. Using a spatula or palette knife, carefully flip it over and continue to cook for about 1 more minute - or until golden brown on both sides. Then turn and cook the edges until golden - they should take around 30 seconds each.
Meanwhile, make the chocolate whipped cream: pour the double cream into a medium-sized bowl. Sift in the cocoa powder and add a drizzle of maple syrup, followed by a pinch of sea salt. Whisk until you have medium peaks. Taste and adjust the sweetness/saltiness, as necessary.
Pop onto a plate and slice in half. Serve with a dollop of the chocolate whipped cream, a drizzle of hazelnut creme and a handful of fresh raspberries, if desired.