Begin by making the set orange curd, take the 200ml of orange juice and boil it in a saucepan until it has reduced to 100ml and is concentrated. Leave to one side to cool a little.
Take the gelatine and place it in a bowl of cold water to soften.
Whisk together the eggs and sugar in the bowl of a stand mixer until they are light and fluffy. Add half the reduced orange juice to the bowl and whisk again briefly.
Return all of the mixture to the saucepan and cook the curd over a low heat, stirring continuously for 5 mins until it starts to thicken.
Remove the pan from the heat, squeeze the excess water from the gelatine and then stir the gelatine into the curd until completely dissolved.
Strain the curd through a sieve into a bowl and while still warm stir in the softened cubed butter piece by piece until it is melted and incorporated into the curd.
Take a 16cm loose bottomed cake tin and spread a layer of cling film in the bottom of the tin and up the sides. Pour the curd into the lined tin and spread the curd out evenly. Take another piece of clingfilm and press it to the surface of the curd so that it is touching it, this will stop any condensation or a skin forming. Place the curd in the fridge to set.
Next make the praline feuilletine layer, take the chocolate and place it in a bowl over a pan of simmering water. Melt the chocolate until it reaches 45C, you may find you still have some small pieces of chocolate, remove it from the heat and keep stirring until all of the chocolate has melted.
Stir in the hazelnut praline paste and then the feuilletine, take another 16cm loose bottomed cake tin and spread a layer of cling film in the bottom of the tin and up the sides. Spread the praline feuilletine into the tin in an even layer and again press a piece of clingfilm gently to the surface. Place this in the fridge to set. Make sure nothing is exposed as the chocolate will absorb the moisture in the fridge.
Next make the genoise, take a 23cm cake tin and line with baking parchment and grease the sides of the tin.
Place the eggs and sugar in the bowl of a stand mixer and then place this over a pan of boiling water. Whisk until the mixture reaches a temperature of 37C. Remove the bowl from the heat, return it to the stand mixer and whisk until the batter has reached ribbon stage.
Take the flour and gently fold it through the egg and sugar mixture, when the flour is two thirds folded through take two spoonfuls of the mixture and stir it into the melted butter.Return the butter mixture to the egg and sugar mixture and stir until the flour is completely mixed in.
Pour the batter into the prepared cake tin and bake in an oven preheated to 190C Fan for 15 minutes until golden brown and the sponge springs back when pressed gently.
Leave the cake in the tin to cool for about 10 mins, then run a knife around the edge and release the cake from the tin. Place the cake on a rack to cool and when cooled remove the greaseproof paper and wrap in clingfilm, save it for use later. The cake can be frozen or stored in an airtight container.
Next make the cointreau syrup, put the sugar, water and vanilla extract in a saucepan and bring to the boil. Let the mixture boil for 2-3 minutes and then let it cool completely before adding the cointreau. Store in an airtight container in the fridge for up to a month.
Next make the dark chocolate glaze, soak the gelatine sheets in a bowl of cold water.
Put the water and sugar in a saucepan and bring it to the boil, then allow it to simmer for 2-3 minutes over a low heat. Add the sifted cocoa powder and the cream and whisk to incorporate it all to a smooth mix.
Bring back to the boil and allow it to simmer for another 4-5 minutes. Take the saucepan off the heat and squeeze the excess water out of the gelatine, add the gelatine to the mixture and stir until dissolved.
Strain the glaze into a bowl and then cover with a layer of clingfilm touching the surface to prevent a skin forming. Leave to cool and then place in the fridge for up to 4 days.
Finally when you are ready to assemble the entremet, make the chocolate mousse. Put 150ml of cream in a saucepan with the milk and bring to the boil.
Place the eggs and sugar in the bowl of a stand mixer and whisk for 2-3 minutes until light in colour.
Put the chocolate in a bowl that will be big enough to take the custard as well.
When the milk and cream has boiled, add half of it to the egg and sugar mixture and whisk again until just combined. Return the mixture to the saucepan and cook over a low heat, stirring continuously.
When the mixture is thick enough to coat the back of a spoon and has reached a temperature of around 82-84C remove it from the heat and pass the mixture through a sieve onto the chopped chocolate.
Mix the custard and chocolate together until emulsified and leave to one side to cool.
Place the remaining cream in the clean bowl of a stand mixer fitted with a whisk attachment and whisk it until it forms soft peaks.
Take the whipped cream and gradually fold it into the chocolate custard mixture until it is evenly combined. Place the mousse to one side and begin to assemble your entremet.
To assemble your entremet, firstly ensure you have space in your freezer for the assembled entremet to fit easily into the freezer.
Take a loose bottomed cake tin larger than the 20cm cake ring and line it with a layer of clingfilm, try to smooth it as much as possible. Make sure that you have all of your components close by and you can get to them easily whilst assembling the entremet.
Take the 20cm cake ring and place it on top of the genoise, using a sharp knife cut around the inside of the ring so that the genoise is slightly smaller than the cake ring. Clean any crumbs from the cake ring and make sure it's clean.
Take the 20cm cake ring and place it inside the lined tin. Then take the chocolate mousse and place almost half the mousse in the base of the cake ring. Using a small palette knife spread chocolate mousse up the sides of the cake ring and ensure that the ring is completely covered and you can't see any that isn't covered with mousse.
Spread the mousse in the centre of the cake ring so that it is evenly layered, take the set orange curd and place it in the centre of the cake ring and press down lightly so that there won't be any gaps between the curd and the mousse.
Next take the praline feuilletine and place that directly on top of the set orange curd. Take the remaining mousse and fill in the sides around the set orange curd and praline feuilletine and spread an even layer over the top. You may not need all the mousse, you just need to make sure that enough room remains to add the genoise.
Take the genoise and using a pastry brush soak it with the cointreau syrup, place it inside the cake ring and press it down gently so there aren't any gaps. Place the entremet in the freezer to set overnight.
The next day, take the entremet and remove it from the freezer and gently peel away the bottom layer of the loose bottomed cake tin along with the clingfilm. Place the entremet on a bowl or can slightly smaller than the cake ring with the mousse side facing upwards.
Take a chef's blowtorch and use it around the cake ring to loosen the ring. Careful not to heat it too much, or you will melt the mousse. Gently slide the cake ring from the entremet and place it back on the tin or on a board lined with clingfilm and return it to the freezer.
When ready to glaze the entremet take the glaze from the fridge and heat it gently in the microwave or in a saucepan, just heat it until it is liquid, you don't want it too hot. Allow the glaze to cool until it reaches 35C.
When the glaze is the right temperature, take the entremet from the freezer and balance it on a bowl or glass that is smaller than the entremet and stood on a baking tray to catch the excess glaze. Pour the glaze over the entremet to cover it completely. Very quickly run a palette knife over the surface of the entremet to remove the excess glaze.
Leave the glaze to set for a couple of minutes and then using a sharp knife cut off any straggly bits of the glaze. Transfer the entremet to a plate and decorate with any decorations of your choice. This could be candied or crystallised nuts, candied peel, tempered chocolate decorations, gold leaf, macarons anything that inspires you.
Transfer to the fridge and allow the entremet to defrost, just before serving leave to come to room temperature for 20 to 30 minutes before serving.