Magnificent enough for a summer wedding or anniversary, this glamorous and complex Viennese confection of meringue, whipped cream and summer berries, finished with fondant violets, dates back to the Baroque period of the Austro-Hungarian Empire.
Line 3 large baking sheets with baking parchment. Draw two 20cm circles on two of the trays and one 20cm circle on one of the trays. (You should end up with five 20cm circles). Pre-heat the oven to 120°C/100°C fan/250°F/Gas ½.
For the meringue shell, tip the egg whites and cream of tartar into a large, spotlessly clean bowl and whisk with an electric mixer on high speed until the egg whites form stiff peaks. Add the caster sugar, a tablespoon at a time, whisking continuously to make a thick, glossy meringue.
Spoon two thirds of the meringue into a piping bag fitted with a 1.5cm plain tube. Pipe a thick ring just inside one of the circles drawn on the baking sheet and continue spiralling inwards until the entire circle is filled. Repeat with a second circle. These are the base and the top of the meringue cake.
Repeat the process with the three remaining circles, except don't fill in the circles this time, so you have 3 hoops of meringue. These are the sides of the meringue shell. Bake for 45 minutes. Remove from the oven and leave to cool.
Meanwhile make the fondant violets. For each fondant violet, take 2 little pieces of dusky lavender fondant and 3 small pieces of deep purple lavender and roll them into small balls (about the size of an orange pip). Dust 2 pieces of greaseproof paper with icing sugar then place the balls of fondant between the sheets and flatten each ball out, using your fingers, to a thin circle approximately 1cm in diameter. These form the petals. Roll a tiny piece of yellow fondant into 3 tiny balls to form the stamens.
Using a small paintbrush and a tiny amount of water, stick the petals and stamens together to form a violet; with the 2 dusky lavender petals at the top, 2 dark purple petals below them, and the remaining dark purple petal on the bottom in the middle. Press the yellow stamens into the centre. Repeat to make 13 violets. Leave to dry on greaseproof paper for at least 1 hour.
When the meringues are dry, gently slide one of the cooked, filled meringues onto a 30cm, heatproof (to 120°C/248°F) serving plate. Spoon the remaining meringue into the piping bag and pipe 8 blobs of meringue, evenly spaced, around the edge of the circle. Place one of the meringue hoops on top and press down very gently to stick the hoop to the base.
Repeat the process with the other 2 hoops of meringue. Roughly pipe the remaining one third of meringue around the sides to disguise the hoops. Using a spatula, smooth out the meringue so the sides are smooth and straight and look like a cake. Bake on the serving plate for 45 minutes. Remove from the oven and leave to cool.
For the meringue decoration, set a large mixing bowl over a pan of gently simmering water. Tip the egg whites and sugar into the bowl and whisk until the sugar is dissolved and the meringue reaches 70°C/158°F on the sugar thermometer.
Remove from the heat and continue whisking until cool and stiff. Spoon the meringue into the piping bag fitted with the large star nozzle. Pipe a pretty border around the base, the middle and the top edge of the meringue shell. Then pipe a border around the outside edge and the middle of the meringue circle that will become the top of the meringue cake. Bake for 30 minutes. Remove from the oven and leave to cool.
For the filling, whip the cream and icing sugar together to form soft peaks. Then gently fold in the strawberries and raspberries. Spoon into the cooled meringue cake shell and top with the meringue lid.
To decorate, use tiny blobs of meringue to stick 6 violets on the piped border going around the middle of the cake, 6 violets around the top of the cake and 1 violet in the centre of the top of the cake.