Brush a baking tray with grease in a few places and spread out with parchment paper.
Preheat the oven to 170 °C.
Whisk the yolks with the warm water and salt for about 5 minutes until thick and very creamy. Whip the egg whites with a pinch of salt until not too stiff and add to the egg yolk mixture. Sift the spelt flour over it and gently fold everything together with a whisk. Spread the mixture on the prepared baking sheet and bake on the middle shelf for 12-15 minutes, the surface should be elastic. Pull the parchment paper from the baking sheet and turn the sponge out onto a kitchen towel. Remove the paper and loosely roll up the dough from the narrow side, cool.
Cut the chives into fine rolls, chop the other kitchen herbs. Mix the yogurt, mascarpone and ricotta well in a baking bowl, fold in the kitchen herbs, season with the juice of one lemon, pepper, salt and a little sugar. Set aside 5 tablespoons of the cream.
Unroll the sponge roll and spread the remaining cream evenly on it, roll it up again, wrap it in cling film and leave it in the fridge for a few hours. Then spread the roll with the remaining herb cream and chill again.
Clean, rinse and spin dry the arugula. Clean, rinse and cut radishes into sticks. Stir a vinaigrette from the juice of one lemon, balsamic vinegar, salt, pepper and oil, add the ra