Instructions

1. Melt butter in a stainless steel sauté pan over medium heat, swirling occasionally, until foamy, golden amber, and nutty-smelling (5–8 minutes). Pour into a mixing bowl, including browned bits. Let cool to room temperature.
2. Stir granulated and brown sugars into cooled butter until combined. Set aside to cool completely.
3. In a medium bowl, whisk together both flours, baking soda, baking powder, salt, and espresso powder (if using).
4. Whisk eggs, egg yolk, and vanilla into the butter-sugar mixture.
5. Gradually fold in dry ingredients with a rubber spatula until just combined.
6. Fold in chopped chocolate and toffee bits.
7. Wrap dough in plastic and refrigerate 24–72 hours for best flavor and texture.
8. Before baking, let dough sit at room temperature for 1 hour.
9. Preheat oven to 350°F (177°C). Line baking sheets with parchment paper.
10. Scoop dough into 3-tablespoon-sized balls (use a #20 cookie scoop).
11. Bake for 12–14 minutes, until golden brown and slightly puffed.
12. Immediately after removing from oven, use a round cookie cutter slightly larger than each cookie to gently nudge into perfect circles.
13. Sprinkle with flaky sea salt if desired.
14. Cool on baking sheet for 2 minutes, then transfer to a wire rack.
15. Store in an airtight container at room temperature.