To make the passion fruit curd, put the passion fruit purée into a pan and bring to a slow simmer. Meanwhile, whisk the egg, yolks, sugar and cornflour until smooth and pale. Pour the passion fruit purée over the egg mix, whisking to combine. Scrape the curd mixture back into the pan and cook over a medium heat, whisking constantly, until the mixture bubbles and thickens. Scrape the curd into a bowl and press a sheet of clingfilm onto the surface (this will prevent a skin forming). Chill until needed.
Heat the oven to 180C/fan 160C/gas 4 and lightly butter a deep 20cm round cake tin, lining the base with baking paper.
For the chocolate cake, put the butter and sugars into a large bowl and beat using an electric mixer until light and fluffy. Add the eggs one at a time, beating the first until fully combined before adding the second.
In a separate bowl, mix the flour, cocoa powder, baking powder and sea salt. In a jug, combine the coffee and milk. Mix the flour mixture into the butter mixture 1/3 at a time, alternating with the milky coffee, until fully combined. Scrape into the prepared tin and bake for 35-40 minutes or until the cake springs back when pressed. Allow the cake to cool in the tin for 10 minutes before turning out onto a wire rack to cool completely.
To make the ganache, put the dark and milk chocolate and butter into a bowl. Put the cream into a pan and bring to a simmer, then pour over the chocolate and allow to sit for a few minutes before stirring until smooth. Divide into 2 bowls, one for the filling and one for coating. Set aside until thickened and spreadable.
When ready to assemble, use a large serrated knife to carefully slice the cake into three equal layers (use a ruler to mark up the layers before cutting). Put the bottom layer of cake onto a piece of baking paper and spread the cut side liberally with ½ the curd. Then ½ of the ganache. Repeat with the second layer. Sandwich the two layers together. Spread the remaining reserved ganache over the top and sides of the cake. Put the cake into the freezer for 1 hour. Note: I put 1/3 of the ganache into a piping bag and created a boarder around the top and bottom edges of the cake. I used fresh garden roses and bay leaves to add a touch of summer.
Allow the cake to come to room temperature before serving. This cake will keep in the fridge for 4 days.
