Preheat your oven to 350°F (175°C). Line your baking sheets with parchment paper to ensure easy cookie removal.
In a large mixing bowl, use an electric mixer to cream together the room temperature unsalted butter, granulated sugar, and brown sugar until the mixture is light and fluffy. This should take about 3-5 minutes.
Beat in the large eggs, one at a time, mixing well after each addition. Then, pour in the pure vanilla extract and mix until fully incorporated.
In a separate bowl, whisk together the unsweetened cocoa powder, all-purpose flour, baking soda, espresso powder, and kosher salt. This will ensure that the dry ingredients are evenly distributed.
Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix; it’s okay if there are a few flour streaks remaining.
Using a cookie scoop, portion out the dough onto the prepared baking sheets, leaving enough space (about 2 inches) between each cookie. If you’re using colorful nonpareils sprinkles, now is the time to sprinkle them on top!
Place the baking sheets in the preheated oven and bake for 10-12 minutes, or until the edges are set but the centers are still slightly soft. The cookies will continue to firm up as they cool.
Remove the cookies from the oven and sprinkle with coarse sea salt while they’re still warm. Allow them to cool on the baking sheet for about 5 minutes, then transfer them to a cooling rack to cool completely. Enjoy your delicious Chocolate Butter Cookies with a glass of milk or your favorite beverage!
