For the genoise sponge: Line the base of an 8inch square baking tin (making sure not to grease the sides). Then preheat the oven to 175C/155C Fan. Sift the cocoa and plain flour into a small bowl and set aside. Add the eggs, sugar and salt to a large bowl and using an electric whisk, whisk for 6-7 minutes until tripled in volume, light coloured and a thick rope of mixture falls and dissolves slowly on the surface. Add a third of the flour mixture to the eggs and fold with a spatula until almost combined. Then repeat with the other third of flour, and then the final third. Place the oil into a small bowl, and fold in a quarter of the flour/egg mixture ensuring its fully combined. Pour this mixture back into the flour/egg mixture and fold again until all just combined.
Evenly pour the mixture into the baking tin and bake for 20-22 minutes until the cake has risen and feels firm to touch. Cool for a few minutes in the tin, then take a knife carefully round the edges of the cake to release from the tin and turn out on a cooling rack. Set aside to cool completely.
For the mousse: Place the sugar and 25ml of the water into a small saucepan. Place over a medium-low heat and simmer without stirring, keeping a food thermometer handy. Meanwhile, place the egg yolks into a large bowl and begin whisking with an electric hand whisk on a low speed. Once the sugar syrup has reached 115C take off the heat, and pour down the side of the bowl into the egg yolks. Turn the mixer up to a high speed, and whisk until the mixture is well combined and cooled to room temperature. Then set aside.
Fill a small bowl with water and place in the gelatine leaves to bloom for 10 minutes. Meanwhile, place the peanut butter into a large bowl and mix in the remaining 20ml of water. Then place the honey in a small saucepan and heat over a low heat until lukewarm and runny. Squeeze the water out of the bloomed gelatine and then whisk into the honey. Pour the honey mixture into the peanut butter and mix in well. In a separate bowl, whisk the chilled double cream until very stiff. Then, add the egg yolk mixture into the peanut butter in two increments. Then mix a 1/3 of the whipped cream into the peanut butter mixture well, to lighten it. Then gently fold in the remaining whipped cream and salt, until the mousse is smooth. Set aside.
For the syrup: Place the water, sugar and jam in a small saucepan and set over a medium-high heat. Bring the syrup to a boil, and simmer until the sugar and jam has dissolved. Then set aside to cool slightly. Meanwhile, peel and slice the apricots. (To make peeling easier, blanch the apricots in boiling water for 30seconds, then run under cold water)
To assemble: Line the 8inch baking tin with clingfilm, then place the sponge on top. Using a pastry brush, liberally brush the apricot syrup over the sponge. Then lay the slices of apricot on top. Finally, spread over the mousse and smooth with a palette knife till flat. Then place in the freezer for 1hour to set.
For the glaze: Break up the chocolate into small pieces and add to a small heat-proof bowl with the oil. Melt in 20 second increments in the microwave until smooth. Pour over the chilled mousse and tilt the baking tin to spread evenly. Then place into the fridge for 30 minutes to set.