Toast cumin seeds in a dry pan over medium heat for 2-3 minutes, stirring constantly, until fragrant and slightly darkened. Watch closely to avoid burning. Let cool, then grind into powder using a spice grinder or mortar and pestle.
1 tsp roasted cumin powder
Add mint leaves, cilantro leaves, green chilies with seeds removed, peeled ginger, lemon juice, salt, and roasted cumin powder to a blender or food processor. Pulse 5-6 times to break down large pieces.
1 cup fresh mint leaves, 1 cup fresh cilantro leaves, 1-2 green chili peppers, 1 inch fresh ginger, 2 tbsp lemon juice, 0.75 tsp salt, 1 tsp roasted cumin powder
Blend on high for 20 seconds, scrape down sides with a spatula, then blend again for another 20 seconds. Add 2 tablespoons cold water if mixture won't blend smoothly. The chutney should be thick enough to coat a spoon but not paste-like.
2-3 tbsp cold water
Taste and adjust seasoning by adding more salt, lemon juice, or sugar as needed. Blend for 10 more seconds after each adjustment. If using yogurt for creaminess, stir it in now rather than blending.
1 tsp sugar, 2 tbsp lemon juice, 0.75 tsp salt, 2 tbsp plain yogurt
Transfer chutney to an airtight container and refrigerate for at least 10 minutes before serving. Stir before serving if water separates on top.
