Step 1

Preheat the oven to 350F degrees. Line a 9x13 inch pan with parchment paper, or aluminum foil and lightly grease.

Step 2

In a large bowl, whisk together the melted butter and sugar (or beat with an electric mixer.

Step 3

Whisk in the eggs and vanilla extract. You don't want the butter to look like it's melting out at this point.

Step 4

Stir in the flour, cornstarch and salt, ensuring that there are no flour clumps.

Step 5

Fold in the chocolate chips/ mix-ins.

Step 6

Spoon the batter into the prepared pan and smooth the top.

Step 7

Bake in the preheated oven for 24-28 minutes, or until the top looks set and shiny and an inserted toothpick comes out clean or with a few damp crumbs.*

Step 8

Cool fully before slicing.