This magical illusion dessert will baffle friends and family, and while it might look like a dry, old washing up sponge, the delicately flavoured orange and lemon joconde sponge is as delicious and moist, as it is hyper-realistic.
Preheat the oven to 190°C/170°C fan/375°F/Gas 5. Grease and line 2 x 8” square loose-bottomed cake tins.
For the joconde sponge, whisk the egg whites until stiff and fluffy in a stand mixer fitted with the whisk attachment. Gradually add the caster sugar until fully incorporated.
Sift the ground almonds and icing sugar together in a large bowl. Add the whole eggs and flour to this, then mix to form a batter.
Vigorously beat 1 tbsp of the egg whites into the ground almond batter. Once combined, gently fold the remaining egg white mixture into the batter and then stir through the melted butter.
Separate ⅓ batter and colour green with the gel food colouring, then flavour with the orange zest and orange extract. Pour into one of the lined cake tins.
Colour the remaining ⅔ batter with the yellow gel food colouring, and flavour with the lemon zest and lemon extract. Pour into the other lined cake tin.
Bake both sponges for 15 minutes. Remove the green sponge and bake the yellow sponge for a further 15 minutes. Remove and cool.
Once cooled, peel the baking paper from the yellow sponge and slice a thin layer off the top so that it is level. Spread the apricot jam over the yellow sponge, then flip the green sponge so that the baking paper is on top. Peel away the paper.
Trim the sides of the sponges so they are even, then cut into 6 equal rectangles.
For the lemon syrup washing up liquid, heat the caster sugar, lemon juice and water in a pan and bring to the boil. Soak the gelatine leaf in cold water until soft, squeeze out the excess liquid and add to the pan along with a drop of green food colouring. Stir until the gelatine has dissolved and remove from the heat.
For the soap bubbles, whisk the egg whites until foamy, then add the caster sugar and whisk until dissolved.
Serve the sponges with a dollop of soap bubbles and syrup washing up liquid.