1-First Step: Preheat your oven to 350°F (175°C) and line two baking sheets with parchment or silicone mats. Measure ingredients and use a digital scale for consistency when making these Eggnog Snickerdoodle Thumbprint Cookies. Have your mixer, rubber spatula, cookie scoop, and cooling rack ready.

2-Second Step: In a large bowl, beat 4 ounces of softened unsalted butter with ½ cup light brown sugar and ¼ cup granulated sugar until pale and airy. Proper creaming traps air and helps the cookies rise. Scrape the bowl to fully incorporate ingredients.

3-Third Step: Add 1 medium egg, and 1 teaspoon vanilla extract to the mixture and beat until combined. This step adds moisture and holiday spice to your Eggnog Snickerdoodle Thumbprint Cookies.

4-Fourth Step: Whisk 245 grams all-purpose flour, ¼ teaspoon baking soda, ½ teaspoon cream of tartar, and ¼ teaspoon kosher salt in a separate bowl. Evenly mixed spices ensure consistent flavor.

5-Fifth Step: Add dry ingredients to the wet batter in two additions, mixing on low speed until just combined. Avoid overmixing to prevent tough cookies.

6-Sixth Step: Scoop dough into 1 tablespoon-sized balls and roll in the cinnamon sugar mixture. Place on prepared sheets and press an indentation with your thumb.

7-Seventh Step: Bake for 7 minutes, then gently press down indentations if needed. For uniform results, rotate pans midway.

8-Eighth Step: Combine filling ingredients and microwave in 15-second intervals until melted. Fill each cookie with about ½ teaspoon of ganache and allow to set.

9-Final Step: Allow cookies to cool completely. Store in an airtight container for up to 5 days or freeze for up to 3 months.