Line a fine-mesh strainer with cheesecloth and pour 2 cups plain yogurt inside. Set over a bowl and let drain 30 minutes in the fridge until thickened.
2 cups plain yogurt
Heat a small pan over low heat and add 1 teaspoon cumin seeds. Toast 1-2 minutes, shaking pan frequently, until fragrant but not smoking. Remove from heat immediately.
1 teaspoon cumin seeds
Transfer strained yogurt to a mixing bowl and whisk with a fork until smooth and creamy. Add ½ teaspoon salt, ¼ teaspoon black pepper, and 1 tablespoon fresh lemon juice, whisking after each addition.
2 cups plain yogurt, 0.5 teaspoon salt, 0.25 teaspoon black pepper, 1 tablespoon lemon juice
Fold in ¼ cup finely chopped fresh mint leaves, 2 tablespoons chopped coriander (optional), 1 finely chopped green chili (optional), and 2 tablespoons finely chopped onion (optional). Stir gently to distribute evenly.
0.25 cup fresh mint leaves, 2 tablespoons coriander leaves, 1 unit green chili, 2 tablespoons onion
Cover bowl with plastic wrap and refrigerate 15-30 minutes. Stir once before serving and garnish with extra mint leaves if desired.
0.25 cup fresh mint leaves