• This recipe requires at least 1 hour of chilling the cookie doughs for the best result and flavor. If you can do overnight, you will be rewarded with an even more amazing taste and texture

Prepare the brownie dough:

• I use chocolate chips. If you use chocolate bars, cut into smaller pieces. Fill a small saucepan with about 1–2 inches of water. Place a heatproof bowl (glass or metal) on top, making sure the bottom of the bowl doesn’t touch the water. Bring the water to a gentle simmer, not a rolling boil. Place chopped chocolate or chips and butter in the bowl and stir with a silicione spatula until the just last few bits of chocolate chips still visible, remove from the heat and continue to stir until all of the chocolate and butter are melted
  
• Take the bowl off the pot once melted to prevent overheating. Keep water out of the chocolate, or it will seize and become grainy. Let the chocolate down while you prepare the rest
• In a mixing bowl, combine egg, salt, sugar, and vanilla. Use a balloon whisk to whisk vigorously until the sugar dissolves.
  
• Then add the melted chocolate and whisk again until the mixture is shiny.
  
• Sift in all-purpose flour, cocoa powder, and baking powder. Use a spatula to fold to combine everything. You will get a very sticky dough.
  
• Cover with a plastic wrap and let it refrigerate for a minimum of 1 hour. I let it chill overnight for 8-10 hours, or even up to 2-3 days is fine too if you don't have the time to bake it yet
  

Prepare the chocolate chip cookie dough:

• Combine melted butter, brown sugar, sugar, salt, and vanilla extract in a mixing bowl. Whisk vigorously for about 1 minute until the sugar dissolves.
  
• Add the egg and whisk again and you can see the mixture will emulsify because the egg helps emulsification.
  
• Sift in all-purpose flour and baking soda. Use a spatula to fold and combine.
  
• Before it's fully combined, add the chocolate chips and continue to fold until you no longer see dry bits of flour mix.
  
• Cover the bowl or wrap the dough with a cling wrap and refrigerate in the fridge for a minimum of 1 hour. I let it chill overnight for 8-10 hours, or even up to 2-3 days is fine too if you don't have the time to bake it yet
  

Shaping the dough:

• Preheat the oven to 350 F (180 C) for conventional oven. Please lower the temperature by 20 F (15 C) if using convection oven. Line two baking sheets with parchment paper
• The doughs are cold now and easy to work with. Use a spoon to scoop about 1 tablespoon of brownie dough, about 15 grams if you weigh (I did).
  
• You can roll it into a dough ball. Repeat with the rest. I get about 19 dough balls
  
• Portion out 20 grams of chocolate chip dough (a bit over 1 spoonful). You can roll it into a dough ball. Repeat with the rest. I get about 19 dough balls
• You can take one brownie dough and one chocolate chip cookie dough and put them together and roll into a dough ball
  
• Or you can divide the brownie dough into 2 and the chocolate chip cookie dough into 2. Arrange them in a criss-cross pattern. Then roll them into a dough ball
  
• There is no right and wrong here. I just keep the dough half and half for each cookie
• Place them on the baking sheets, about 2 inches apart because they will spread some
  
• Press on few more chocolate chips on the dough. Sprinkle with a bit of flaky sea salt if you want
  

To freeze unbaked cookie dough:

• Place the unbaked dough balls in the freezer for about an hour to let them harden but not fully frozen yet. Then transfer to a freezer container or freezer bag. They can be kept frozen for up to 2 months. When ready to bake, do not thaw and bake from frozen. Just need to add a minute or two to the baking time

Bake:

• I strongly suggest to bake one tray at a time. Place the baking pan in the middle rack. I keep the other tray in the fridge while waiting for the oven
• Bake for 10-12 minutes. The edges should be just lightly brown. Do not overbake these cookies. They appear very soft when they just come out from the oven
• If the cookies are not round in shape, you can use the back of the spoon to push the edges of the cookies to make it rounder. This has to be done immediately while they are still warm
  

Cool down:

• Let the cookies cool down on the baking pan. The cookies are puffy when they are just out of the oven.
  
• They will flatten a bit as they cool down, creating some shiny crackles on the brownie portion
  

Storage:

• They can be kept in an air-tight container for 2-3 days at room temperature. They also freezes very well after baked. Simply let them cool down completely and then place them on a baking sheet, not touching each other and put them in the freezer for about 1 hour. This will harden the cookies. Transfer to a freezer bag or container and freeze for up to 1 month.
• Simply thaw at room temperature for a few minutes. If you want that fresh-baked cookies feel, I reheat in a toaster oven at 320 F for 3-5 minutes to let the chocolate melt slightly