Stir the fat until foamy. Stir in sugar, lemon peel and salt. Dice marzipan and stir into the fat-sugar mixture until smooth. Gradually add the eggs. Mix flour and baking powder.
Stir in the milk by the spoonful. Grease the bottom of a springform pan (26 cm Ø). Fill in the dough, smooth it down and bake in a preheated oven (electric: 200 °C/ gas: level 3) for 15-20 minutes.
Remove the base from the springform pan and let it cool down. Lightly brown ground hazelnuts in a pan without fat while turning. Pour onto a plate and allow to cool. Also lightly roast the hazelnut leaves.
Sort the blueberries, rinse with cold water and dab dry. Whip cream, sugar and vanilla sugar until stiff. Fold in ground hazelnuts and 2/3 of the berries. Spread blueberry cream on the base. Sprinkle with the remaining berries, crumbled meringue and roasted hazelnut leaves.
Decorate as desired with mint leaves. Makes about 12 pieces.