Peel and slice the cucumber in half lengthways, scrape out the seeds then grate the remaining cucumber.
Place the grated cucumber in a sieve and rest it on a bowl. Give it a little stir, and leave to drain. If you're in a rush, you can get rid of the excess moisture by pushing the liquid out with the back of a spoon.
Combine the cucumber with plain soya yogurt, lemon juice and pressed garlic cloves. Finely chop the dill and mint, then fold through the cucumber mixture. Season with salt to taste.