1. First make the blackberry sauce toripple through the mallow.
2. Put the berriesand 1 tsp sugar in a small bowl and coverwith cling film. Microwave for 30 secs onHigh. Alternatively, add 1 tsp water thensoften in a pan over a low heat. Mashwell until saucy, then leave to cool.
3. Heat oven to 160C/140C fan/gas 3.Grease and line the base and sides of a23cm square traybake tin, leaving someoverhang. Using electric beaters or ahand whisk, beat the butter and sugar ina large bowl until very pale and creamy,then beat in the egg and yolks, followedby the vanilla.
4. Mix the flour, almonds,baking powder, nutmeg and a pinch ofsalt, then fold into the fluffy mix to makea very thick batter.Fold in the apple, then spoon into thetin and smooth over the top. Scatter withthe blackberries, poke them in just alittle, then bake for 45 mins until goldenand a skewer inserted into the middlecomes out clean. After removing, leavethe oven on.For the mallow topping, you’ll need alarge piping bag with a 1cm nozzle, or afood bag with a corner snipped off.
5. Whiskthe egg whites, lemon juice and a pinchof salt to stiff peaks.
6. Add the sugar1 tbsp at a time, whisking well after eachspoonful, to make a shiny, stiff meringue.Ripple with the cooled blackberry mix,then spoon into the bag. Pipe 16 evenlyspaced, walnut-sized meringues on topof the cake (you’ll have some left over),scatter with the toasted almonds, thenbake for 10-12 mins until the meringuesare just set. Cool in the tin for 30 mins,then remove to a rack to cool completely.
7. Add a dusting of icing sugar, if you like,then cut into squares.