Step 1: Place the chopped white chocolate and 1/2 cup of the heavy cream in a heat-proof bowl. Set over a pot of simmering water (double boiler) and stir until completely smooth.
Step 2: Remove the chocolate mixture from heat and stir in the vanilla bean paste and sea salt. Let it cool to room temperature, ensuring it is no longer warm to the touch but still liquid.
Step 3: In a separate chilled bowl, whip the remaining 1.5 cups of heavy cream until stiff peaks form. Be careful not to over-whip into butter.
Step 4: Gently fold one-third of the whipped cream into the cooled white chocolate mixture to lighten it up. Then, fold in the remaining whipped cream until no white streaks remain.
Step 5: Spoon or pipe the mixture into 6 small glass cups or ramekins. Smooth the tops or create decorative swirls.
Step 6: Refrigerate the cups for at least 4 hours, or overnight, to allow the mousse to set completely. Garnish with berries before serving.