This dessert looks impressive, but it’s far easier to make than you would expect from my long and detailed instructions. The dessert is light and not too sweet, and is perfect as the last course of a feast.
The cake needs several hours in the fridge to set, so if you like, bake and assemble it the day before you plan to serve it. To make it, you need a cake ring that is 18cm (7 in) in diameter and at least 5cm (2 in) high; if you don’t have one, use a springform pan (minus the base) with the same dimensions.
The cake batter is the same one used for ladyfinger biscuits, although when baked, the result is different from the commercial types, which are crisp and dry. For the dessert, the batter is piped into three cake layers, rather than into long, slender ladyfinger shapes.
The recipe calls for two types of white chocolate. The first, used in the mousse, is “real” white chocolate – often labelled as couverture. It’s made with cocoa butter and the packaging will always state the amount it contains – usually 25 per cent to 35 per cent. The decoration is made with chocolate coating, often labelled as compound chocolate (or compound coating); it contains vegetable shortening instead of cocoa butter.
For the matcha (green tea powder), there’s no need to use the super-expensive ceremonial-grade quality, but do buy one that you are willing to drink because the colour will be more vivid than the type usually labelled for desserts.
Preheat the oven to 180° C (350° F). With the cake ring as a guide, use a marker pen to trace three 18cm (7 in) circles on a sheet of parchment that fits your oven tray (you might need to use more than one tray). Turn the parchment over, so the ink side is down.
Place an 8mm (⅜ inch) plain piping tip in a piping bag. Just above the top of the piping tip, twist the bag tightly and then use your thumb to insert it into the tip (this prevents the cake batter from flowing out of the bag when you fill it).
Separate the four eggs, putting the yolks into a large mixing bowl and the whites into a medium-size mixing bowl. Add the fifth egg white into the bowl with the yolks.
To the bowl with the four yolks and one white, add the baking powder, vanilla extract and 100g (½ cup) of sugar. Immediately start beating the ingredients with an electric hand mixer (or a heavy-duty mixer fitted with the whisk attachment). Beat the ingredients until they are thick and pale yellow; when you lift the beater/s and drizzle the mixture back into the bowl, it should stay briefly on the surface before sinking into the rest of the batter.
Add the flour to the bowl and mix on low speed until it is fully incorporated.
Remove the beater attachments from the hand mixer (or whisk attachment from the heavy-duty mixer) and wash them thoroughly in hot, soapy water to remove any trace of fat. Dry the beaters/whisk.
Use the mixer to whip the four egg whites, cream of tartar and salt until frothy. With the machine on medium speed, add 55 grams (¼ cup and 1 tsp) of sugar in a slow, steady stream. Beat the whites on high speed until they form medium-soft peaks.
Add one-third of the egg white mixture to the egg yolk/flour and use a rubber spatula to mix vigorously until smooth. Add the remaining whites in two additions, folding them in gently to maintain as much volume as possible.
Scrape the mixture into the prepared piping bag and twist the top tightly. Untwist the part of the bag that is in the tip. Starting at the centre of each traced circle, pipe the batter in a continuous, concentric circle to make three 18cm (7 inch) layers. (If there’s any leftover batter, pipe it out into ladyfingers; eat them soon after they are baked.)
Bake the layers at 180° C (350° F) for about 10 minutes, or until fragrant and pale golden; when you touch the surface, it will spring back without leaving an indentation. Cool to room temperature.
Make the syrup. Put the sugar in a bowl and add 90ml (¼ cup and 2 tbsp) of boiling water, then stir until dissolved. Use a small sieve to sift the matcha into the syrup and whisk until smooth.
Remove the cake layers from the parchment paper. If necessary, trim them so they fit into the cake ring. Set aside the most attractive layer for the top of the cake. Place the cake ring on a perfectly flat serving plate or cake stand and put one of the cake layers in it.
Brush the bottom layer thoroughly with the tea syrup. Flip the two remaining layers over and brush their bottoms with some of the syrup.
Slice the raspberries in half. Lay half of them over the bottom cake layer.
Make the mousse. Put 20ml (4 tsp) of room-temperature water into a small bowl. A little at a time, sprinkle the gelatin over the water, letting each addition absorb fully before adding more.
Put the white chocolate in a medium-size mixing bowl. In a saucepan, heat 160ml (⅔ cup) of cream until simmering, then pour it over the chocolate. Add the gelatin/water and stir the ingredients until smooth.
Use a small sieve to sift the matcha into the white chocolate, then whisk until fully incorporated. Cool to room temperature.
Whip 190ml (¾ cup plus 4 tsp) of chilled cream until it forms soft peaks. Add about one-third of the cream to the white chocolate and mix in thoroughly. Add the remaining cream in two additions, folding it in gently to maintain as much volume as possible.
Pour half of the mousse mixture into the cake ring and smooth out the surface.
Place the middle cake layer top-side up on the mousse. Press gently, then brush with the tea syrup. Place the remaining raspberries on the cake layer then top with the rest of the mousse and smooth out the surface. Put the nicest cake layer, top-side up, in the ring and press gently so it’s level. Refrigerate for at least six hours.
Melt the white coating/compound chocolate, either in the microwave (stir every 30 seconds until 80 per cent melted, then stir so the remaining chocolate melts in the residual heat) or over a double boiler (place the bowl over hot – but not boiling – water and stir almost constantly until 80 per cent melted, then stir so the remaining chocolate melts in the residual heat; dry the bottom of the bowl).
Pour the melted coating chocolate onto a 30cm x 12cm (12 inch x 4 ¾ inch ) strip of parchment. Use a small palette knife to spread it almost the length of the strip. Use a small sieve to lightly dust matcha over the white chocolate, then chill until hard.
Loosen the chilled cake from the cake ring. Insert a small, sharp knife with a flexible blade (or a small palette knife) between the ring and the cake and go around the entire perimeter of the cake. Carefully lift the ring away. If necessary, clean the serving plate, scraping away any mousse that might have leaked out.
Use a small sieve to lightly dust matcha powder over the cake, then decorate it as you like with raspberries or strawberries.
Break the chilled white chocolate coating into uneven shards that are a little taller than the cake. Place them around the perimeter of the cake, pressing so that they adhere.
When cutting the cake, don’t try to slice through the white chocolate shards; remove them before cutting each piece, then replace them when you serve it.