Add the eggs one at a time, mixing well after each addition.

Stir in the vegetable oil and vanilla extract until fully incorporated.

In a separate bowl, whisk together the cocoa powder, plain flour, cornstarch, and a pinch of salt.

Gradually add the dry mixture to the wet mixture, stirring until just combined. Be careful not to overmix.

Gently fold in the milk chocolate chips and white chocolate chips until evenly distributed throughout the batter.

Pour the brownie batter into the prepared baking pan, smoothing the top evenly.

Bake in the preheated oven for about 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (not wet batter).

Once done, remove the brownies from the oven and allow them to cool in the pan for about 10-15 minutes.

Then transfer them to a wire rack to cool completely before slicing into squares.

Enjoy your delicious chocolate chip brownies! These are great warm, but they also taste fantastic at room temperature or chilled.