** Make the mousse a day in advance.
Prepare the mousse: combine the white choc chocolate, 100ml of cream, and salt in a microwave-safe bowl. Microwave in 30-second increments, stirring every 30 seconds, until the chocolate has melted and the mixture is smooth.
Pour it into a large bowl, and let it cool to room temperature, stirring occasionally.
While you wait for the chocolate mixture to cool, prepare the gelatin. Whisk together the gelatin and the cold water in a small bowl, and set it aside to let the gelatin absorb the water. When the chocolate is at room temperature, microwave the bowl of gelatin for 15 seconds, until it is melted. Whisk the melted gelatin and chocolate together.
Whip the remaining 1 cup heavy cream to soft peaks. Add the dulce de leche and whip until you reach stiff peaks. Fold half of the whipped cream into the chocolate, and once it’s incorporated, gently fold in the remaining whipped cream.
Pour the mixture into your silicone molds and allow them to set overnight. To remove them gently cut the very top of the opening using a sharp knife and invert the mousse out of the molds as shown in the video.