Preheat your oven to 350 degrees
In a large bowl, beat 1 cup of room temperature butter with 2/3 cup of granulated sugar and 3/4 cup of brown sugar until creamy
Add 2 large eggs, 1 egg yolk and 2 teaspoons of vanilla extract and continue whipping until fully incorporated
Using a mesh sifter, sift 1 1/2 cups of bread flour, 1 cup of all purpose flour, 1 tablespoon of espresso powder, 1 teaspoon of baking soda, 1/2 teaspoon of baking powder and 1/2 teaspoon of salt into the mixing bowl and mix until just combined
Fold in 1 1/4 cup of crushed toffee and 8 ounces of chocolate chunks
Place rounded tablespoons of cookie dough onto non-stick or parchment lined baking sheets 2 inches apart
Bake the cookies in a 350 degree oven for 8-10 minutes or until the edges just begin to brown
Transfer the baking rack onto a heat proof surface and let the cookie cool for 5 minutes before transferring them directly onto the cooling rack to continue cooling
Sprinkle the cookies with flaky sea salt
Store fully cooled cookies in an air tight container at room temperature