Preheat your oven to 350°F (175°C). Line your baking sheets with parchment paper for easy removal of the cookies.
In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and sea salt.
In a large mixing bowl, cream the unsalted butter, light brown sugar, and granulated sugar together until light and fluffy, about 3-4 minutes.
Mix in the espresso powder, then add the eggs one at a time, followed by the vanilla extract, mixing until well incorporated.
Gradually add the dry ingredients to the wet mixture, mixing on low speed until no streaks of flour remain.
Gently fold in the chocolate chunks and toffee bits until evenly distributed throughout the dough.
Using a cookie scoop, drop rounded tablespoons of dough onto the prepared baking sheets, spacing them about 2 inches apart. Sprinkle a pinch of flaked sea salt on top of each cookie.
Bake for about 10-12 minutes, or until the edges are golden and the centers look slightly underbaked.
Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to a cooling rack to cool completely.
