Halve cucumbers, and scoop out seeds using a melon baller or small spoon. Grate cucumbers on the large holes of a box grater. Transfer the grated cucumbers to a colander set over a bowl or in the sink. Stir in 2 teaspoons salt, and let the cucumber mixture stand 15 minutes to drain.
Rinse cucumbers; shake out excess liquid. Wrap in a clean kitchen towel; squeeze out as much liquid as possible.
Stir together cucumbers, yogurt, feta, chopped mint, cream, and lemon juice. Season with salt and pepper. If desired, transfer dip to a bowl lined with cabbage leaves. Garnish dip with mint sprig; serve with crudites.