Chocolate Mousse Brownies



For the Brownie Layer:
Soft butter, for greasing the pan
4 large eggs
2 cups sugar, sifted
8 ounces / 2 sticks melted butter
1¼ cups cocoa, sifted
2 vanilla beans, seeds only
⅓ cup flour, sifted
½ teaspoon kosher salt

For Chocolate Mousse:
10 ounces milk chocolate, finely chopped
2½ cups whipping cream, chilled
7 grams gelatin
2 tablespoons of water