Put the mint leaves, cilantro, green chili, and garlic in a mini chopper. Blitz it until you get a slightly rough paste of herbs.
In a bowl, pour the yogurt and add the green paste. Season it with salt and black pepper.
Using a fork or a spoon, mix the yogurt until the herbs everything is well mixed. Taste it and add more seasoning if needed.
Notes
Sometimes the yogurt is thicker than usual. In this case, you add a spoon or two of milk.
If you can not get ordinary natural yogurt, a Greek-style yogurt is equally good. Though I find it a bit too thick and not tangy enough. So I would put lemon juice of half lemon and a tablespoon of milk.