In a large heavy saucepan, whisk milks, cream, milk powder, cardamom, sea salt and, if desired, saffron until blended. Cook over low heat until mixture thickens slightly, about 15 minutes, stirring constantly. Do not allow to boil. Remove from heat. Strain through a fine-mesh strainer into a small bowl; cool., Stir in cashews, pistachios and extract. Transfer to six 4-oz. ramekins. Cover and freeze for 8 hours or overnight. If desired, serve with additional nuts.