Place 1 cup of butter in a saucepan over medium heat. Stir every 30 seconds as it melts and begins to foam. Continue cooking until it turns a rich golden brown and releases a nutty aroma, about 5–6 minutes. Remove from heat, pour into a mixing bowl, and let cool for 30 minutes.
Once cooled, add the brown sugar and white sugar. Whisk on high for 2–3 minutes until light and combined.
Add the hot coffee (or water), eggs, and vanilla extract. Whisk again for about 2 minutes until smooth.
Add the flour, baking soda, salt, chocolate chips, and toffee pieces. Mix until fully incorporated, being careful not to overmix.
Scoop the dough into ¼–⅓ cup portions and place into a covered container. Refrigerate for 12–24 hours.
When ready to bake, preheat the oven to 375°F. Place cookies a few inches apart on a baking sheet.
Bake for 16–20 minutes, until the edges are set and the centers remain slightly soft.
Let cool, then enjoy!
