Rinse leafy greens in cold water, shake off. Place in a saucepan and cover with 2 cups of cold water. Put on fire, bring to a boil and cook over medium heat for 30 minutes. Throw on a sieve and wipe or chop in a blender, cool.
Peel cucumbers and grate. Finely chop the dill and green onion. Put the cucumbers, dill and green onions in a bowl, salt and rub with a wooden spoon to release the juice.
Pour the cucumbers with kvass, add the grated greens and mix. Put ice in a bowl.
Arrange slices of coho salmon on plates and fill with botvinia.