Prepare the sponge cake with the following variations: If using the coconut flavoring, reduce the vanilla extract to one teaspoon and add the coconut flavoring. Stir in one cup of the toasted coconut after stirring in the flour. Divide the batter among two greased, floured, Gefen Parchment-lined nine-inch round pans. Bake for about 30 to 35 minutes, rotating the pans halfway through baking, until the centers feel set when lightly pressed.

Meanwhile, prepare the coconut custard (see below).

When the cakes are completely cooled, whip the cream with the confectioners’ sugar and vanilla until stiff peaks form.

Place one cake layer in the bottom of a trifle dish. Spread half the custard over the cake. Spread a thick layer of cream over the custard. It’s a bit tricky to spread cream over custard—you can dollop spoonfuls all over the custard and then “connect the dots,” or pipe the cream evenly over the custard using a piping bag with a large tip.

Repeat with the second layer of cake and rest of custard. Dollop remaining whipped cream over the top. For a more decorative topping, pipe the cream in large whorls or rosettes over the entire surface. Sprinkle the remaining coconut on top. Refrigerate until ready to serve.

Combine the sugar, cornstarch, and salt in a medium saucepan. Stir in the coconut milk and mix to dissolve all the ingredients. Cook on a medium-low flame, just until the mixture starts to get hot and steam.

Temper the egg yolks by slowly pouring half a cup of the hot mixture into them while whisking vigorously. Slowly pour the yolk mixture into the pot while stirring constantly. Continue to cook and stir until the mixture is thick and bubbling. Remove from the heat and stir in the vanilla.

Strain the custard through a fine-mesh sieve into a bowl, pushing down with a rubber spatula, to get rid of lumps. Cover the surface with plastic wrap. Cool to room temperature, then chill completely in the refrigerator.