Chop the chocolate bar into small pieces and place them in a mixing bowl.

Heat the whole milk in a saucepan.

Meanwhile, zest the clementines over the chocolate and squeeze the juice from two clementines onto the chocolate as well.

Gradually pour the hot milk over the chopped chocolate, whisking to combine until the mixture is smooth.

Set aside.

In a mixing bowl that has been chilled in the freezer, whip the cold heavy cream until it forms soft peaks.

Using a spatula, gently fold part of the whipped cream into the chocolate mixture.

Then pour the chocolate mixture over the remaining whipped cream and gently fold to combine.

Spoon the clementine chocolate mousse into small glasses or a serving dish; chill in the refrigerator for at least 2 hours.