Preheat oven to 350°F (175°C). Line a 9x13 inch baking dish with parchment paper, allowing it to overhang the sides for easy removal.

In a large bowl, whisk together the flour, cornstarch, cocoa powder, baking powder, and salt. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, combine the eggs, granulated sugar, melted butter, and vanilla extract. Beat on medium speed until the mixture is light and fluffy.

With the mixer off, gradually add the dry ingredient mixture to the wet ingredients. Turn the mixer on low speed and mix until just combined and no dry streaks remain.

Pour the brownie batter into the prepared baking dish and spread evenly. Bake for 30-35 minutes, or until the edges are set and the center is still slightly moist and glossy.

Let the brownies cool completely in the baking dish on a wire rack.

Once the brownies have cooled, spread the prepared strawberry cheesecake mousse evenly over the top. Garnish with fresh strawberries before serving.