Preheat oven to 325°F. Spray a 8X8 inch pan with non-stick baking spray. Line the bottom and 2 sides of the pan with parchment paper.
In a medium bowl, sift together the flour, cocoa powder, cornstarch, and salt. Set aside.
Using a mixer with a whisk attachment, blend the eggs, egg yolk, and sugar together on high for 5 minutes. The eggs will be pale in color and fluffy.
Melt the butter in the microwave for 1 minute or until melted. Add the melted butter, oil, and vanilla to the egg mixture. Mix until combined. Take off mixer.
Add all of the dry ingredients into the bowl. Use a rubber spatula to gently fold in the dry ingredients. Be careful to not lose any air from the eggs. Fold in the chocolate chips.
Pour into the pan. Bake for 35-40 minutes. The edges should be set and the middle is slightly underdone.
Allow to cool completely in the pan. Then, place in the freezer for 10 minutes. This will make it easier to cut into. Cut the brownies into 9 squares. Cut 5 of those squares into brownie bites for the ice cream.