Wash 250 grams of seedless grapes thoroughly and pat them dry. Set aside a few grapes for garnishing.
In a blender, add the grapes, 500 grams of chilled plain yogurt (dahi), 2 tablespoons of sugar, and a pinch of salt. Blend until smooth and creamy.
Taste the lassi and adjust the sugar according to your preference. If the lassi is too thick, add a little cold water or milk to adjust the consistency.
Pour the grape lassi into serving glasses. Garnish with the reserved grapes and a few mint leaves (optional).
Serve the grape lassi chilled.