Step 1: Preheat the Oven
Preheat oven to 350°F. Line a baking sheet with parchment paper.
Step 2: Mix the Wet Ingredients
In a mixing bowl, whisk the browned butter, dark brown sugar, and white sugar until glossy. Add the egg yolk and vanilla extract, then whisk again until smooth.
Step 3: Combine the Dry Ingredients
Add the all-purpose flour, baking soda, and salt. Mix on medium speed (or by hand) until just combined. Avoid overmixing.
Step 4: Fold in the Good Stuff
Stir in the chocolate chunks, crushed toffee pieces, and a pinch of espresso powder if using. The dough should be thick, soft, and slightly sticky.
Step 5: Let the Dough Rest
For best results, cover the dough with plastic wrap and let it rest for about 15 minutes at room temperature.
Tip: You can also portion into cookie dough balls and freeze for later.
Step 6: Bake to Perfection
Scoop 6–8 balls of dough using a cookie scoop and place on a parchment-lined baking sheet. Space them well.
Bake for 9–11 minutes, or until golden brown around the crisp edges and just set in the center. Let cool on the pan for 5 minutes, then transfer to a wire rack.