Wash the limes with hot water, pat dry, finely grate the peel and squeeze out the juice. Halve the chili peppers lengthways, remove the core and dice them very finely (!) (The recipe is based on 2 small Thai chilies).
Mix the yogurt with the sour cream, chilli cubes, powdered sugar, lime juice and lime zest well.
Pour the mixture into small glasses and place in the freezer. Take out the glasses 15 minutes before serving and sprinkle with chopped pistachios on top.