Preheat oven to 350F and grease an 8x8 baking pan or line with parchment paper
Gently melt butter and chocolate bar together in the microwave or over a double boiler
Add eggs, brown sugar, and vanilla extract to a large mixing bowl or a stand mixer
Mix with the whisk attachment for an electric stand mixer or with an electric hand mixer until the mixture is fluffy and lighter in color about 3 minutes
Fold melted chocolate and butter mixture into the eggs and sugar mixture with a spatula - be sure the chocolate mixture is not too hot
Add cocoa powder and salt to the bowl and fold in with a spatula. Add the chocolate chips and fold in again
Mix with a spatula until you are left with a smooth, even mixture
Pour brownie batter into a baking pan
Bake at 350F for 28 minutesÂ
Allow to cool completely and then slice into squares
Notes
Whip eggs and sugar for a crackly top - to get a delicious crackled top that you know and love, be sure to whip the eggs and brown sugar until frothy and light in color. I like to use an electric hand mixer for this and mix for a minimum of 3 minutes.
Allow to cool completely before cutting - I know it can be SO tempting to dive into a warm plate of brownies, but these flourless brownies are fragile so it is essential to allow them to cool completely before cutting. That gives them time to set and stay together.
Use a plastic knife to cut into squares - if your brownies always stick to your knife while you are cutting them, try using a plastic knife! For some reason the plastic knife makes clean cuts with much less sticking than a standard metal knife.
Store leftovers in the fridge - for an extra fudgy texture that is simply irresistible I like to store any leftover brownies in an airtight container in the refrigerator.