Preheat oven to 350° F.
Beat the butter in a stand mixer at medium speed until creamy. Add the sugar and cream together. Lower the speed and add the eggs, one at a time, beating until just blended.
Add the cocoa and vanilla. Beat on low speed for 1 minute until blended. Gradually add flour, beating well. Stir in chocolate chips.
Pour batter into a greased 13 x 9" baking pan. Bake 30-35 minutes (I put mine in for 35 minutes in the glass dish and got a goopy but stable middle - it might reach this stage more quickly if you use a metal pan). Cool completely before cutting into squares. (I totally sneaked a bite early, but it does pay to let the bulk of them cool, because then they don't stick to the knife.) Happy baking!