• Preheat oven to 350°F. Line a baking sheet with parchment paper and set aside.
• In a small mixing bowl combine the flour, baking soda, salt and cardamom. Set aside.
• Using a stand mixer fitted with a paddle attachment, beat the butter and 1 cup of sugar until light and fluffy. Add the egg and vanilla and beat just until blended.
• Reduce the speed to low and mix in the flour mixture in 3 additions. Scrape sides as needed.
• Combine the cinnamon and remaining ⅔ cup of sugar in a small shallow bowl. Set aside.
• Roll the dough in 1 inch balls (about 1+ heaping teaspoon) and place 2 inches apart on the parchment lined baking sheet.
• Bake until the edges are firm, about 10-12 minutes.
• Remove and allow the cookies to cool for 1 minute then place each in the cinnamon sugar mixture, turn and coat both side. Transfer to a wire rack and cool completely.
• Roll remaining dough into balls but be sure to place on a cool cookie sheet to prevent excessive spreading.

FOR THE FILLING:

• Melt the butter in a small saucepan over medium heat. Whisk in the cinnamon and cardamom and stir until fragrant, about 1 minute. Remove from the heat and add the dulce de leche until blended. Spread 1 (scant) tablespoon of the dulce de leche mixture on the bottoms of half the cookies. Top with the remaining cookies to form a sandwich. Gently press to spread the filling to the edges.
• Store in an airtight container for 3 days at room temperature or in the refrigerator until served.