In a saucepan, melt the butter over medium heat, stirring consistently. Continue for 5-8 minutes until butter is foaming and browned. You'll see browned bits floating in the butter. Butter should be caramel in color. Don't let it go too long or else the brown butter will have a burnt flavor.
Combine the hot butter and both sugars into a large bowl. Whisk together to combine and let sit to cool
Sift together the flour, baking soda, baking powder and coffee crystals in a separate bowl or container.
Once the butter mixture is cooled to room temperature, whisk in the eggs, egg yolk and vanilla.
Slowly add the flour mixture into the butter mixture using a spatula. Once combined pour in the chopped chocolate and toffee bits.
Scoop the dough onto a parchment lined tray. You should get 20-22 cookies from this recipe.
Cover the tray with plastic wrap and refrigerate for no longer than 24 hours. Refrigerating for a longer period of time will result in dry cookies.
Preheat oven to 350 degrees. When you're ready to bake, place scooped cookies onto a parchment lined baking sheet with 2 inches of space between each.
Bake for a total of 12 minutes, making sure to turn the pan half way in the baking time.
Once removed from the oven , you can sprinkle with flaky salt and let cool for a few minutes before moving to a cooling rack.
For storage, keep in an airtight container for up to 3 days.
