Add butter to a large glass bowl. Pour chocolate chips on top. Microwave for 90 seconds and stir until all chocolate chips are melted. Return to microwave for 15-30 seconds longer, if necessary.
Add brown sugar and sugar to the bowl. Stir to combine.
Add eggs and vanilla. Mix well.
Gently stir in cocoa until completely mixed in.
Add in flour. Stir in.
Pour brownie mixture into a greased 9×13 glass pan. Use a spoon to smooth the brownie batter to the edge of the pan.
Bake at 350 degrees for 25 minutes.
Allow to cool slightly before serving, but serve warm for the maximum level of gooey-ness!
Allow to cool completely for firmer brownies that are still amazingly delicious.
Serve with ice cream on top, if desired.
Notes
This recipe can be baked in a smaller 8×8 pan, for 38 to 40 minutes, if you prefer thicker gooey brownies.
Cooled brownies that have firmed up can be microwaved for 10 to 20 seconds to become gooey again.