Start by melting unsalted butter in a medium saucepan over medium heat. Stir continuously for about 5-7 minutes until the butter transforms into a golden brown color and emits a nutty aroma. Remove from heat and mix in espresso powder for a delightful coffee kick. Transfer the mixture to a bowl and let it chill in the refrigerator for 1-2 hours, until firm.

Once your brown butter is chilled, beat it together with granulated sugar and brown sugar in a large mixing bowl using an electric mixer. Mix on medium speed for 3-4 minutes until the mixture is light and fluffy.

Next, blend in a large egg and vanilla extract into your sugar mixture. Continue mixing on low speed until smooth and fully combined.

In a separate bowl, whisk together all-purpose flour, baking powder, baking soda, and salt. Gradually add the dry mixture to the wet ingredients, mixing on low speed until just combined.

Gently fold in the Heath toffee bits using a spatula, ensuring that they're evenly distributed throughout the dough.

Scoop the cookie dough into large balls using a cookie scoop, placing them onto a tray lined with parchment paper. Refrigerate the dough balls for at least 2 hours.

Preheat your oven to 350°F (175°C) while the dough chills. Once ready, arrange the chilled cookie dough balls on a lined baking sheet. Bake for 11-13 minutes or until the edges turn golden brown.

After baking, let the cookies cool on the baking sheet for about 5 minutes. Then, carefully transfer the cookies to a wire rack to cool completely.