Melt the white chocolate, butter and a pinch of salt in a microwave safe bowl in 20-30 second increments, stirring in between, until smooth and melted.
8 oz. white baking chocolate, chopped (look for a high quality baking bar)., 3 Tbsp. unsalted butter, room temperature, pinch of salt
Allow the white chocolate to cool for a few minutes. Then whisk in the egg yolks, one at a time, until combined. Set aside.
3 large eggs, yolks and whites divided
Beat the egg whites and sugar for about 4-5 minutes on medium-high speed just until firm (but not stiff) peaks form.
1/3 cup granulated sugar
Gently fold in about ⅓ cup of the egg white mixture into the chocolate mixture with a rubber spatula. Repeat until all egg whites are added. Set aside.
Beat the heavy cream until stiff peaks form, but don't make butter!
1 cup heavy cream, chilled
Gently fold the whipped cream into the white chocolate mixture just until combined.
Divide into 4 glasses and refrigerate for at least 6 hours or ideally overnight.
Prior to serving, make the homemade whipped cream. Add the cream, powdered sugar and vanilla to the bowl of a stand mixer with the whisk attachment. Beat on medium-high speed until medium peaks form, about 3-4 minutes.
1 cup heavy cream, chilled, 2 Tbsp. powdered sugar, 1 tsp. vanilla extract
Add the whipped cream and fresh berries on top of the mousse and serve immediately. Enjoy!