In a medium saucepan, melt the butter over medium heat, stirring constantly until golden brown, about 5–7 minutes. Remove from heat and refrigerate until solidified, about 1 hour.

Once solidified, beat the browned butter with granulated sugar and brown sugar on medium speed until light and fluffy, about 3-4 minutes.

With the mixer running on low, add in the egg and vanilla extract, mixing just until smooth.

In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. Gradually add this to the wet ingredients, mixing on low speed until just combined.

Gently fold in the toffee bits using a spatula to ensure even distribution.

Portion the dough into large balls and refrigerate for at least 2 hours, or up to 24 hours.

Preheat your oven to 350°F (175°C) about 15 minutes before baking.

Place dough balls on a lined baking sheet, sprinkle with sea salt, and bake for 11-13 minutes until edges are golden brown.

Let cookies cool on the sheet for about 5 minutes before transferring to a wire rack.