Preheat oven to 350 degrees F. Prepare a 8x8 pan by greasing sides and bottom.
In a medium mixing bowl sift together cocoa powder, gluten-free flour, baking soda and cornstarch. Whisk in sugar and salt.
Creating a well into the center of dried ingredients, add whisked eggs, melted butter, olive oil and vanilla extract. Mix together until fully combined. Fold in chocolate chips. Pour into prepared baking pan.
Bake for 23-26 minutes, or until toothpick comes out clean.
Allow to fully cool before frosting the brownies.
Gluten Free Chocolate Frosting
Add softened butter in medium bowl. Beat butter with mixer until creamy (30-45 seconds), add vanilla extract, 2 Tablespoons milk, continue beating with mixer, slowly add powdered sugar 1/2 cup at a time incorporating into butter mixture.
Add cocoa powder. If frosting is too thick, beat in more milk very slow.