Begin by melting 1 cup of unsalted butter in a medium saucepan over medium heat. Stir constantly for about 5-8 minutes, until the butter turns golden brown and releases a nutty aroma. Be attentive to avoid burning it. Once perfectly browned, transfer the butter to a bowl and let it cool slightly.

Stir in 2 tablespoons of espresso powder into the warm browned butter until dissolved. Using an electric mixer, add 3/4 cup of brown sugar and 1/2 cup of granulated sugar. Beat the mixture on medium speed for about 3-4 minutes, until light and fluffy, creating a delicious base for your Brown Butter Coffee Toffee Cookies.

Crack one large egg into the mixture along with 1 teaspoon of pure vanilla extract. Mix on low speed until the ingredients are fully combined and the batter appears smooth and creamy. This step will enhance the cookies' flavor and help create that delightful chewy texture.

In a separate bowl, whisk together 2 cups of all-purpose flour, 1 teaspoon of baking powder, 1/2 teaspoon of baking soda, and 1/2 teaspoon of salt. Gradually add this dry mixture to the wet ingredients, mixing on low speed until just combined. Avoid overmixing to ensure your Brown Butter Coffee Toffee Cookies remain tender and chewy.

Gently fold in 3/4 cup of Heath toffee bits using a spatula until they are evenly distributed throughout the cookie dough. This will add a delightful crunch and a sweet touch to complement the coffee flavor. Be careful not to overmix, as you want to keep the dough light and airy.

Scoop the dough into balls, approximately 1.5 tablespoons each, and place them on a lined baking sheet. Cover the dough with plastic wrap and refrigerate for at least 1-2 hours, or even overnight if possible. Chilling the dough enhances flavor and helps prevent excess spread during baking.

Preheat your oven to 350°F (175°C). Once the dough has chilled, place the cold cookie balls on a lined baking sheet, leaving space in between for spreading. Sprinkle lightly with flaky sea salt and bake for 11-13 minutes, or until the edges are golden and the centers are slightly soft but set.

After baking, allow the cookies to cool on the baking sheet for about 5 minutes. Then, transfer them to a wire rack to cool completely. This cooling process helps maintain that chewy texture and ensures your scrumptious Brown Butter Coffee Toffee Cookies are perfect for serving.