Melt the butter and chopped chocolate (or chocolate chips) together in a bowl. You can use the microwave or a double boiler. If using the microwave, simply microwave the mixture for 30 second intervals, whisking in between.
Whisk until smooth and melted together.
Add the brown sugar to the chocolate/butter.
Whisk until incorporated.
Add the egg and vanilla, and whisk until smooth.
Add the flour, cocoa powder, and salt to the bowl. It’s best if you pre-sift the dry ingredients before adding them, or sift them right into the bowl.
Mix until combined.
Cover the bowl with a piece of plastic wrap and place it in the fridge for about 2 hours, so it firms up.
Chocolate Chip Cookie Dough
Cream the butter with a mixer for 2 minutes on medium high speed.
Add brown sugar and white sugar. Cream for another 2 minutes until light in color and fluffy.
Add the egg and yolk to the mixer.
Cream until incorporated. Add the vanilla extract. Mix to combine.
Add flour, baking powder, baking soda, and salt to the bowl. Mix with a spatula or on the lowest setting to incorporate the flour.
Last but not least, add the chocolate chips and stir to combine.
To assemble
Grab about 2 tablespoons of chocolate chip cookie dough and flatten it out with your hands. Grab about 1 tablespoon of brownie batter and place it in the middle of the cookie dough.
Gently roll both of them together into a smooth ball.
Place the formed cookies on a baking sheet and put the tray in the freezer or fridge.
Put them in the freezer for 15 minutes before baking. Or put them in the fridge for 30 minutes before baking.
If you don’t want to bake all cookies at once, place them in the freezer, once they are solid, after about 2 hours, transfer them to a zip loc bag, and keep it in the freezer for up to 2 months.
You can also keep the cookies in the fridge for a couple of days before baking, make sure to cover them.
Bake the cookies straight from the freezer or fridge, no need to thaw or let it come to room temperature. It’s actually way better to bake the cookies when they are cold.
To bake
Pre-heat oven to 350ºF. Place 5 cookies on a baking sheet, about 3 inches apart.
Bake for about 12 minutes.
Remove the cookies from the oven when they look slightly golden on the outside, but still soft.
The cookies will continue to cook after they come out of the oven. As a rule of thumb you always want to remove the cookies from the oven before they actually look baked, otherwise they will be dry and tough as they cool down.
You can also top the cookies with chocolate chips when they come out of the oven.
Storage
Store the frozen cookies for up to 3 months, in a ziplock bag. Store the baked cookies at room temperature for up to 4 days, in an air tight container.
Notes
Butter: feel free to use salted butter, reduce the salt amount to 1/4 tsp if doing so in the Chocolate Chip Cookie Dough. And to the brownie batter, add just a pinch of salt instead of the whole 1/4 tsp.Chocolate: for the chocolate I used semi-sweet chocolate, feel free to use dark or milk chocolate.