Brown the butter: Melt the butter in a light-colored skillet over medium heat, stirring until browned and fragrant, then cool for 5 minutes.

Whisk in the brown sugar and granulated sugar into the brown butter, followed by the eggs and vanilla. Set aside.

In a large bowl, whisk together the flour, baking soda, and salt. Combine wet and dry ingredients, adding chocolate chips and toffee, stirring until combined.

Scoop dough into balls (about 1.5 tablespoons each) and chill the dough balls in the refrigerator for 2 hours, or up to 3 days.

Preheat oven to 350°F (177°C). Line baking sheets with parchment paper or silicone mats.

Place dough balls on baking sheets 3 inches apart. Optionally sprinkle with coarse sea salt and press down slightly.

Bake for 12-13 minutes or until edges are lightly browned. Cool on baking sheets for 5 minutes before transferring to a wire rack.

Enjoy the cookies fresh or store covered at room temperature for up to 5 days or in the refrigerator for 1 week.