In the bowl of a stand mixer fitted with the paddle or using a mixing bowl and hand mixer, cream together butter and sugar for 3-4 minutes.
14 tablespoons unsalted butter, 1/2 cup granulated sugar
Add flour, cardamom, and salt, and mix on low to incorporate, then increase to medium-low and continue beating until the dough comes together. It will look very dry at first, but continue to mix until it clumps and cleans the sides of the bowl. Set aside.
2 1/3 cup all-purpose flour, 1 teaspoon ground cardamom, 1/4 teaspoon fine sea salt
In a small bowl, stir together the brown sugar and cinnamon. Cut the 2 tablespoons butter into small pieces and mix it into the brown sugar until you have a paste.
1/4 cup packed brown sugar, 1 teaspoon ground cinnamon, 2 tablespoons unsalted butter
Using your fingers, pinch small pieces of the paste into balls (about the size of a pea) and scatter into the shortbread dough. Make sure to move the dough around so the paste is evenly distributed.
Once all of the paste is in the bowl, gather the dough together and firmly shape into a log about 12 inches long and 2 inches in diameter. Place on a large piece of plastic wrap.
Sprinkle 1 tablespoon of the pearl sugar down the length of the dough. Using the plastic wrap to help you, roll the dough onto the sugar, gently pressing to adhere. Unwrap and turn dough, then repeat the process until all the sides are covered. Don't worry if some of the sugar falls off; we're not aiming for perfection.
1/4 cup pearl sugar
Wrap the dough in the plastic and chill in the refrigerator for 30 minutes.
When ready to bake, preheat then oven to 350°F and line two baking sheets with parchment paper.
Remove the dough from the fridge and cut it in half. Place one half on a cutting board and return the rest to the fridge. Cut the dough into 1/2-inch slices and arrange on 1 baking sheet. They can be close together as shortbread doesn't spread much.
Bake for 8-10 minutes, until edges and bottoms are pale brown. Do not overbake. Let rest on the baking sheet 2 minutes before transferring to a wire rack to cool completely. Repeat with remaining dough on the second baking sheet.
Notes
Using a scale to measure the flour and sugar will give you the best results (hit Metric next to Ingredients). If you don't have a scale, be sure to spoon and level the flour, do not scoop directly into the flour, or your cookies will be too dry.
Baking the cookies on cold sheets one sheet at a time so they brown evenly and don't spread too much.
This recipe makes approximately 36 cookies when shaping into a 2-inch-diameter log.