Place yeast and 1 tsp sugar in a bowl with 200ml lukewarm water. Stir to combine and set aside for 5 minutes or until frothy.
Place flour and remaining 50g sugar in the bowl of a stand mixer with the dough hook and make a well in the centre of the flour mixture. Whisk eggs into yeast mixture, pour into the well and stir to combine. Knead on medium speed for 2-3 minutes until a dough forms. With the motor running, add butter, 1 piece at a time, until fully incorporated. Knead for a further 8-10 minutes until dough is smooth.
Transfer dough to a greased bowl, cover with plastic wrap and set aside for 1 hour 20 minutes or until doubled in size.
Preheat oven to 170°C. Grease a 20cm round cake pan and line the base with baking paper. Deflate the risen dough to release the air and knead into a smooth ball. Sprinkle the work surface with flour, roll out the dough using a rolling pin. Form a disc of 20 cm and 2 cm thick.
Place dough in the centre of the prepared pan and set aside for 20 minutes to proof. Bake for 50 minutes or until a skewer inserted in the centre comes out clean.
Combine the gelatin powder with 2 tablespoons of cold water. If using gelatin sheets, soak in cold water.
Meanwhile, for the creme patissiere, whisk egg yolks, sugar and cornstarch in a heatproof bowl until smooth. Place milk and vanilla in a saucepan over medium heat and bring to just below boiling point, then remove from heat. Pour hot milk mixture over egg mixture, whisking slowly until combined. Return mixture to the saucepan and place over medium heat. Cook, stirring constantly with a whisk, for 5-6 minutes to get a thick custard. Add the dissolved gelatin powder or the gelatine sheets without the water to creme patissiere and whisk until completely dissolved. Strain into a clean bowl, cover surface directly with plastic wrap and cool to room temperature, then refrigerate until cold.
Whisk crème patissiere until smooth. Transfer to a piping bag fitted with a wide fluted nozzle and chill until ready to use.
For the topping, combine butter, sugar, honey and a pinch of salt in a small saucepan. Cook over medium heat for 2-3 minutes until melted and combined. Stir in almonds, then set.
To assemble, use a large serrated knife to slice brioche in half horizontally. Pipe crème patissiere over the cut side of one half of brioche, then top with other half.
Reheat the topping over medium heat until almond are golden brown at which time, pour over the surface of the cake. serve immediately.