Prepare the cucumber. Using the coarse holes of a box grater, shred the cucumber. You should have about 1 cup. Place the cucumber in the center of a clean tea towel, and squeeze out excess moisture. Set aside.
Blend the base. Combine the soaked cashews, water, lemon juice, and garlic in a blender and blend until smooth and creamy, about 1 minute.
Mix the tzatziki and chill. In a mixing bowl, stir together the cucumber, cashew cream, dill, mint, salt, and pepper. Refrigerate for at least one hour. As it cools, the mixture will thicken and the flavors will meld. Serve, drizzled generously with extra-virgin olive oil.
