Preheat the oven to 350°F/180°C.
Line the pan with parchment paper and grease it will oil. Melt the chocolate in a microwave-safe bowl, stirring every 30 seconds until smooth.
Transfer the chocolate to a large bowl, add oil, and mix well.
Stir in sugar, eggs, and salt. It is important to work quickly so that the eggs do not harden from the heat of the chocolate.
Add cornstarch and mix until everything is combined.
Spread batter into the prepared pan and flatten the mixture with a spatula. The mixture will be very thick and that is OK. Bake for 25 to 35 minutes. Brownies should be puffed and beginning to crack at the edges but still soft to the touch (a toothpick stuck in the center comes out with moist chocolate crumbs).
Let your brownies cool completely in the baking tray.
Slice into squares and enjoy!