Mont Blanc layer cake

Serves: 10
Ingredients
For the meringue:
Medium eggs, egg whites only 5
Caster sugar 200 gm
Icing sugar 125 gm
For the filling:
Chestnut puree, tinned, unsweetened 300 gm
Double cream 350 ml
Ricotta 150 gm
Vanilla pod, seeds only 1
Sugar To taste
Dark chocolate, melted 75 gm
For the orange sauce and segments:
Oranges 5
Orange juice 250 ml
Sugar 4 tbsp
Butter 15 gm
Method
For the meringue:
Cover three baking trays with foil. Using  a lightly buttered pastry brush, trace the outline of an 18cm circle on each foil- covered tray, as a guide for each of the three meringues. This recipe requires that you bake all three at the same time. If your oven has only two shelves, you'll need to squeeze three smaller circles onto two trays instead.
Place the caster sugar on a baking tray lined with baking paper. Warm caster sugar in the oven at 180°C for approximately 5 minutes. Remove the warmed sugar and turn down the oven to 140°C.
Using an electric whisk, beat the egg whites to a stiff froth in a clean, dry bowl. Add a third of the warmed caster sugar to the whites. Whisk thoroughly on high speed until the grains are dissolved. Repeat this process two more times until all the caster sugar is added and the whisked mixture is thick and glossy. (The warmed sugar helps to cook and thicken the meringue more quickly, keeping it stable.) Sift and fold in the icing sugar until the mixture is smooth. Then place a third of the meringue mix onto each prepared foil circle and spread into an even thick disc with a spatula.
Bake at 140°C for about 90 minutes or until the crust is firm and slightly beige. Remove and set aside to cool.
For the filling:
In a bowl, gently beat the chestnut purée to soften and break it up. Add 250 ml of the double cream, ricotta, vanilla seeds and enough sugar to sweeten. Beat the mixture until it's very thick.
For the assembly:
Peel one cold meringue from the foil and place on a flat plate. Spread with a half of the chestnut cream mix and then drizzle melted chocolate over the top. Place the second meringue on top of the first, and repeat the last step with the chestnut cream and chocolate. Lastly, top with the remaining meringue to complete the layer cake. Whip the remaining 100 ml double cream until thick. Fill into a piping bag fitted with a star nozzle. Pipe small rosettes onto the top of the cake, creating little peaks. Then drizzle over with more melted chocolate.
For the orange sauce:
Zest one orange, before peeling it and the rest of the oranges, removing the segments from all. Warm a non-stick pan until hot. Place the orange segments in the pan and caramelise using their natural sugars. In a saucepan, mix together the orange juice, sugar and zest, bring it slowly to a gentle boil and reduce to 2/3. Add the butter to thicken and finish the sauce.
Serving suggestion
Serve with the caramelised orange segments and a drizzle of orange sauce.