In a heatproof bowl, combine the chocolate chips, butter and 2 1/2 tablespoons sparkling grape juice. Set the bowl over a pot of simmering water and stir until the chocolate is melted; let cool.
In another heatproof bowl over simmering water, whisk the egg yolks, sugar and remaining 2 1/2 tablespoons juice until thick and warm but not cooked, 3 to 5 minutes. Remove from the heat and whisk in the melted chocolate; let cool to room temperature.
Using an electric mixer, whip the heavy cream until soft peaks form; transfer 1/4 cup to a small bowl and refrigerate. Let the remaining cream stand until it reaches room temperature, then, using a large rubber spatula, fold into the chocolate mixture until smooth. Spoon into glasses and refrigerate until ready to serve.
Stir the raspberry jam into the remaining 1/4 cup whipped cream and top each mousse with some of the raspberry cream.
