Snickerdoodle Party Cookies

Name: Snickerdoodle Party Cookies
Ingredients: 1 cup (2 sticks) unsalted butter; 2 cups all-purpose flour; 1 tsp. baking soda; 1 tsp. kosher salt; 2½ tsp. ground cardamom, divided; 2 tsp. ground cinnamon, divided; 1 cup (packed) light brown sugar; ½ cup granulated sugar, divided; 2 large eggs; 1 tsp. vanilla extract or paste; 2 1.4-oz. chocolate toffee bars (preferably Skor), finely chopped; 3 cups cornflakes, lightly crushed; Gold or rainbow disco or luster dust (for serving; optional)