Preheat oven to 180C (350F) and grease a 12-hole standard muffin or patty tin.
In a stand mixer, whisk eggs and sugar for 8 minutes until thick, pale, and tripled in volume.
Sift cornflour, custard powder, cream of tartar, and bicarbonate of soda twice, then gently fold into the egg mixture.
Fold in the melted butter until just combined, ensuring no deflation of the batter.
Distribute batter evenly into the prepared tin and bake for 12 to 15 minutes until the sponge springs back when touched.
Transfer cakes to a wire rack to cool completely.
Dissolve raspberry jelly crystals in boiling water and refrigerate for 45 minutes until the liquid is cold and slightly syrupy but not set.
Dip each cooled cake into the jelly to coat the exterior, then immediately roll in desiccated coconut.
Place coated cakes on a tray and refrigerate for at least 2 hours to allow the jelly to set firmly.
Whip the heavy cream with icing sugar and vanilla extract until stiff peaks form.
Cut a horizontal slit into the side of each cake and pipe the cream delight into the center.
Serve chilled for optimal texture.