Step 1: Begin by reducing the apple cider. In a small saucepan, bring 1 cup of apple cider to a gentle simmer over medium heat. Continue to cook, stirring occasionally, until the liquid reduces to 1/4 cup, which typically takes about 10-15 minutes. Set aside to cool completely.
Step 2: Next, brown the butter. In a light-colored saucepan, melt the unsalted butter over medium heat. Continue cooking, stirring frequently, until the butter develops an amber brown color and a rich, nutty aroma. Immediately pour the browned butter into a heatproof bowl to stop the cooking process and allow it to cool to room temperature.
Step 3: In a medium bowl, whisk together the all-purpose flour, baking soda, baking powder, cornstarch, ground cinnamon, and salt. Ensure all dry ingredients are well combined, then set aside.
Step 4: In a large mixing bowl, using an electric mixer, cream together the cooled browned butter, 1 cup of granulated sugar, and light brown sugar until the mixture is light and fluffy.
Step 5: Add the large egg to the creamed mixture and beat until just combined. Stir in the vanilla extract and the completely cooled, reduced apple cider.
Step 6: Gradually add the dry ingredient mixture to the wet ingredients. Mix on low speed until the flour is just incorporated, being careful not to overmix the dough. A few streaks of flour are acceptable.
Step 7: Cover the cookie dough tightly with plastic wrap and chill it in the refrigerator for a minimum of 30 minutes. This step helps the flavors meld and prevents the cookies from spreading too much during baking.
Step 8: Preheat your oven to 375°F (190°C). Line one or two baking sheets with parchment paper for easy removal.
Step 9: Scoop the chilled dough into balls, about 1.5 to 2 tablespoons each. Place them approximately 2 inches apart on the prepared baking sheets.
Step 10: Bake the cookies for 8-10 minutes, or until the edges are lightly golden and the centers still appear soft. They will firm up as they cool.
Step 11: While the cookies are baking, prepare the cinnamon sugar coating. In a shallow bowl, combine the remaining 1/4 cup granulated sugar and 1 tablespoon ground cinnamon.
Step 12: As soon as the cookies come out of the oven, immediately roll each warm cookie in the cinnamon sugar mixture until it is thoroughly coated.
Step 13: Transfer the coated apple cider cookies to a wire rack to cool completely. Enjoy these delightful fall treats!