Peel and wash the carrots and kohlrabi and cut them into thin sticks about 5 cm long. Mix with approx. 1⁄4 tsp. salt and let it stand for approx. 10 minutes. Clean and wash spring onions and cut them into approx. 5 cm long strips.
Clean, wash and pat dry the radicchio. Cut the leaves into thin strips as well.
Mix sour cream and wasabi and season with salt. Debark the toast. Carefully roll out the slices one by one between cling film with a dough roll, making them a little thinner. Spread with wasabi sour cream.
Dab the strips of vegetables slightly dry. Spread the lettuce strips along the bottom edge of the toast about 2 cm wide, letting the strips protrude both left and right over the slice of bread. Roll up the slice of bread tightly.
Wrap each roll tightly in foil and chill for at least 1 hour. Remove foil to serve. Cut each roll into 3 equal pieces.