Chocolate layer cake with Bavarian cream and ganache

Break up the chilled pastry cream with a whisk; fold in some whipped cream to make a Bavarian cream, and flavour it with ganache to taste.

Thaw the frozen cake and split it in half with a serrated knife into two layers (three if baked in an eight-inch pan).

Set the first layer on the cake stand and brush with coffee syrup, concentrating on the drier edges.

Pipe a circle of whipped cream around the border; spread a very thin layer of ganache in the centre with an offset spatula; fill with an even layer of Bavarian cream.

Set the second layer on top and brush lightly with syrup; pipe a circle of whipped cream on top and spread the leftover Bavarian cream inside it.

Freeze 20 to 30 minutes to set.

Warm the ganache in the microwave in 10-second increments until pourable (about 15 seconds here); pour over the top until it drips down the sides.

Let the ganache set, about 10 minutes at room temperature if the cake is cold, or in the refrigerator or freezer.

Pipe rosettes of the remaining whipped cream on top.