BROWNIE CHUNKS

1. Once the brownie has chilled, remove from the pan, remove the parchment paper, and slice into small cubes using a sharp knife. Transfer to a parchment paper lined small sheet pan or plate, and place into the freezer while you are preparing the rest of the cookie dough. They don't get fully solid in the freezer but it helps them to keep their shape when it comes time to add them to the cookie dough.

COOKIES

1. Place the butter in a medium saucepan, and place over medium heat. Cook until the butter has melted, and then continue to cook, stirring frequently and swirling the pan often, until the butter foams up and then goes golden and nutty - it will make a bit of noise and then foam and go quiet just before it is done. This should take 3-4 minutes.
2. Measure out 95g of the brown butter into a medium mixing bowl. Set aside for 10-15 minutes to cool to avoid it scrambling your eggs. Alternatively you can place the bowl into a larger bowl of cold water and stir as it cools down - a little bit warm is fine, you just don't want it to be hot. 
3. Once the butter has cooled, add the brown sugar, granulated sugar, egg, and vanilla. Whisk until the mixture has thickened and lightened slightly in colour. 
4. Add the flour, salt, baking powder, and baking soda. Mix until almost incorporated with a spatula. I like to leave a few flour streaks that will get incorporated when the chocolate chunks are added. 
5. Add the chopped chocolate and frozen brownie chunks and mix to incorporate. Stir it carefully to avoid squishing too many of the brownie chunks. 
6. Line a small sheet pan or container with parchment paper (this is to chill the cookie dough in so an airtight container will work here too). 
7. Using a #24 cookie scoop (2.5 tbsp), scoop balls of cookie dough (Mine weighed about 55g each). Arrange on the lined sheet pan or container (they can be touching). I just leave mine as scoops but you can roll into balls if you like. I got 14 dough balls.
8. Cover with plastic wrap or a lid, and chill the dough for at least 30 minutes. 
9. 10 minutes into the chilling period, preheat the oven to 350°f / 180°c. Line two sheet pans with parchment paper. 
10. Arrange 6 cookie dough balls on a pan, spacing evenly. I like to bake mine one pan at a time and generally do 6 on the first pan and then 8 on the second once I know how much they spread.
11. Bake the cookies for 13-14 minutes, until they are set around the edges and on top and lightly golden brown. Bake longer if you prefer your cookies a little more crispy on the edges. 
12. Remove from the oven, and if desired, using a cookie cutter slightly larger than the cookies, 'scoot' them into a perfectly circular shape if they have gone a little wonky in the oven. 
13. Sprinkle with flaky sea salt if using. Leave to cool on the pan for 10-15 minutes and then transfer to a wire rack to cool completely. 
14. Repeat the process with the remainder of the cookie dough balls. 
15. Store in an airtight container at room temperature for up to 4 days.