Salt, flour, powdered sugar, almonds, peeled, ground mix peel of the lemon, directly add sour apple, halved core peel, grate on the Bircherraffel directly to the amount.
Add the ice-cold butter to the grater, grate everything together quickly between your fingertips until crumbly.
Add egg whites and knead without kneading to form a dough. Form 2 rolls of 4-5 cm ø and wrap in foil to cool for 1 hour. Plums per 12 pieces put 3 plums aside. Cut the remaining fruit in half and remove the seeds. Cut off fruit and bring to a boil with the sugar in a wide frying pan with the lid on. Soften the plums uncovered. The fruit should no longer have any juice. Finely crush and cool.
Whip sugar, cream, very stiff. Pour cold plum puree through a sieve to the whipped cream. Mix carefully.
Lemon balm or mint, fresh Cut each roll of dough into about 18 slices, just under 1 cm thick. Place on a baking sheet lined with parchment paper. Leave to cool for 10 minutes. Preheat oven to 180 degrees. Bake the sablés in the middle of the oven for approx. 15 min. Cool down.
Cut plums in half, remove seeds and cut into very fine slices. Cover each 2 sablé bottoms with wedges, spread with plum cream, lay on top of each other and cover with a third sablé. Garnish with plums and lemon balm.