Grease a large baking sheet; set aside. In a 2-quart microwave-safe* bowl, combine sugar, corn syrup, salt, and cardamom. Microwave, uncovered, on 100-percent power (high) for 6 minutes, stirring once halfway through cooking time.
Stir in cashews, pistachios, pecans, and butter. Microwave, uncovered, on high for 2 minutes or just until mixture turns golden (mixture continues to cook and becomes more golden when removed from the microwave).
Quickly stir in baking soda and vanilla. Spread thinly and evenly on the prepared baking sheet. Let cool. Break into pieces. Arrange candy pieces in gift tin; cover with plastic wrap.