Preheat the oven to 170C and prepare the brownie size tin.
Separate egg whites and yolks. Whisk the whites until stiff and slowly add sugar while still whisking.
Add egg yolks one by one and continue mixing after each one.
Gently fold in sifted flour and baking powder to the egg mixture.
Pour to the prepared tin and bake for 25min. Don't open the oven door in the initial phase of baking to prevent sponge from collapsing.
When ready, cool down in the tin.
Peel the apples, take the cores out and chop roughly.
Stew the apples with a splash of water to prevent sticking. Add sugar and cinnamon. When apples are hot, add the jelly powder and mix to dissolve completely.
Leave to cool and pour over cold sponge base. Put in the fridge for about 30 min until apple jelly mix sets and firms up a little.
Whip the cream with mascarpone, vanilla and sugar until stiff.
Spread on the cold apple layer of the cake. Sprinkle chocolate and cinnamon on top.
You can use different jelly flavours, but I like lemon as it gives additional sharpness to the apples. If you can't find powder jelly (any polish shop will have it under the name 'galaretka'), you can use the solid version and dissolve in apples as well. Alternatively you can use gelatine.