Preheat your oven to 350°F (175°C) and grease a 9×13-inch baking pan.
In a large mixing bowl, melt the butter and sugar together over low heat, stirring until smooth, then remove from heat and stir in the eggs one at a time, mixing well after each addition, then fold in the cocoa powder, flour, vanilla extract, and salt until combined.
Pour the brownie batter into the prepared baking pan and spread evenly, then bake for 25-30 minutes or until a toothpick inserted in the center comes out with moist crumbs, and allow the brownies to cool completely in the pan.
In a separate bowl, beat the softened butter until creamy, gradually add powdered sugar while continuing to mix, then blend in the melted chocolate and vanilla extract, and finally add the pasteurized eggs one at a time, beating well after each addition until the mixture is smooth and fluffy.
Once the brownie base has fully cooled, spread the French silk topping evenly over the brownies and refrigerate for at least 2 hours to set the topping.
Once set, cut the brownies into squares, top them with whipped cream and chocolate shavings, and serve.