Brown the Butter: In a medium saucepan over medium heat, melt 1 cup of unsalted butter until golden brown, about 5 to 7 minutes. Stir continuously. Remove from heat and stir in 2 tablespoons of espresso powder. Cool slightly and transfer to the refrigerator until solid, about 30 minutes.

Prepare the Dough: Beat the chilled brown butter with 1 cup each of packed brown sugar and granulated sugar using an electric mixer on medium speed for 3 to 4 minutes until light and fluffy.

Add Egg and Vanilla: Lower the mixer speed and add 1 large egg and 1 teaspoon of vanilla extract until just combined, about 30 seconds.

Incorporate Dry Ingredients: Whisk together 1 teaspoon of baking powder, 1 teaspoon of baking soda, ½ teaspoon of sea salt, and 2 cups of all-purpose flour. Gradually add to the wet ingredients, mixing on low speed until just combined.

Fold in Toffee Bits: Gently fold in 1 cup of Heath toffee bits using a spatula.

Chill the Dough: Portion out the dough into ¼ cup balls on a parchment-lined baking sheet. Cover and refrigerate for at least 3 hours, preferably 24 hours.

Preheat Oven: 15 minutes before baking, preheat oven to 350°F (175°C) and line another baking sheet with parchment.

Bake the Cookies: Place chilled dough balls on the prepared baking sheet, spacing 2 inches apart. Bake for 11 to 13 minutes until edges are golden brown.

Cool and Serve: Allow cookies to cool on the baking sheet for about 5 minutes, then transfer to a wire rack to cool completely. Serve warm.