Preheat the oven to 350°F. Line a 9×13-inch baking dish with parchment paper up the sides.
In a large bowl whisk flour, cornstarch, cocoa, baking powder, and salt. Set aside.
To the bowl of a stand mixer fitted with the paddle attachment, add the eggs, sugar, butter, and vanilla. Beat on medium speed until light and fluffy.
With the mixer off, add the flour mixture. Turn the mixer on low and mix until the ingredients are well combined.
Pour brownie batter into the prepared baking dish and bake for 30-35 minutes, or until done. Fudgy brownies are done baking when the edges appear set, but the center is still shiny, or moist.
Let the brownies cool at room temperature.
Spoon the mousse over the cooled brownies and spread it into an even layer. Garnish with fresh strawberries