1-First: brown the unsalted butter in a skillet over low heat until it turns amber with brown flakes and smells nutty, then cool it in a heatproof bowl until solidified, about 1 hour. This step is crucial as it builds the rich base for your cookies.

2-Next, whisk together the dry ingredients: 2 ½ cups all-purpose flour, 1 teaspoon baking soda, 2 teaspoons cornstarch, 4 teaspoons instant espresso powder, and ½ teaspoon kosher salt in a bowl.

3-Now, cream the cooled browned butter with 1 cup dark brown sugar and ½ cup granulated sugar until light and fluffy. Mix in 2 large eggs and 2 teaspoons pure vanilla extract until well combined. Gradually add the dry ingredients to the wet mixture, stirring until just incorporated, then fold in ½ cup toffee bits for that sweet crunch.

4-Chilling and Baking Steps: Chill the dough for 1 hour to help with texture and prevent spreading. Scoop about 2 tablespoons of dough per cookie onto parchment-lined baking sheets, spacing them 2 inches apart. Bake at 350°F for 8-10 minutes until the edges are lightly browned.

5-After baking, tap the pans on the counter for crinkly edges and sprinkle with flaky sea salt if you like. Let the cookies cool on the sheets for a few minutes before transferring to a wire rack.