Surprise! The cucumber is actually not a vegetable, but a fruit—a member of the gourd family, relative to the zucchini and pumpkin. Originating in India thousands of years ago, the modern cucumber is available globally in several different varieties, such as the nearly seedless English cucumber; the thin-skinned and ultra-mild Japanese cucumber; the little, round lemon cucumber; and the dill and gherkin variations for pickling. When choosing a cucumber, look for a firm, spot-free fruit and avoid softness and yellow streaks, signs of age. Greenhouses ensure that cucumbers are available year-round, but they're summer fare by nature. But whether you have homegrown or from the market, this snappy seasonal soup is a perfect blend for the cucumber.
Strain the yogurt. To do this, simply line a sieve with clean paper towels and suspend over a bowl. Spoon the yogurt on top of the paper and allow it to drain for 1 hour. Discard the liquid from the bowl.
Place yogurt, 2 cups of cucumber, grapes, and olive oil into a blender and blend at low until smooth.
Strain the cucumber mixture into a bowl, using a spatula to gently stir and press the liquid out of the pulp and through the strainer. Discard pulp.
Stir in chopped mint leaves, salt, and diced cucumber.
Chill before serving.