1. In a small saucepan, heat the cream over low heat. Add the white chocolate pieces, stirring to make the preparation homogeneous.
2. Remove the saucepan from the heat and let the mixture cool for 15 minutes.
3. Whip the cream and strawberry essence with an electric mixer. Add the cream to the chocolate preparation.
4. Divide the mousse into small cups or individual bowls. Place a spoonful of strawberry jam in the center. Fill with the remaining mousse.
5. Refrigerate for 1 hour before serving.