Combine 1 cup granulated sugar and ½ cup light corn syrup in a microwave-safe bowl. Heat in the microwave for 3 minutes. Stir the mixture and heat in the microwave for another 3 minutes. It should start looking amber in color.
Stir in 1 cup chopped cashews. Cook for an additional 3-5 minutes, checking every minute or so to see if the color is a deep golden brown, like a brown paper bag. Don't overcook it and burn the cashews!
Once the mixture is a deep golden brown, remove from the microwave and stir in 1 tablespoon salted butter and 1 teaspoon vanilla extract. Continue cooking for an additional minute. Remove and stir in 1 teaspoon baking soda. It will start to foam and become thick.
Spread the mixture on the buttered baking pan and allow it to cool completely. Break into pieces before storing. Store at room temperature in an airtight container for up to 7 days.