Preheat the oven to 350 degrees F. Bring a kettle of water to a boil over medium heat.
Put the chocolate into a heat-proof bowl. Heat 1 1/2 cups of the cream and 1/4 cup sugar in a medium saucepan over low heat. Whisk just until and sugar is dissolved. Pour the hot cream over the chocolate and whisk until the chocolate is melted and smooth. Put the yolks in a small bowl; while whisking, add a small amount of the warm chocolate mixture to temper the yolks. Whisk the yolk mixture into the chocolate until well combined. Transfer the mixture to a liquid measuring cup for easy pouring.
Put 4 (6-ounce) ramekins into a high-sided baking dish. Evenly fill the ramekins with the chocolate mixture. Carefully fill the pan with the hot water until it reaches halfway up the sides of the ramekins and transfer the pan to the oven. Bake until custards are set but still jiggle slightly in the center, about 30 minutes. Remove the pan from the oven and carefully transfer the custards to a rack and cool to room temperature. Refrigerate the custards at least 2 hours and preferably overnight.
When ready to serve, whisk the cherry jam in a small bowl until loosened and thin. In another bowl with a clean whisk, whip the remaining 1/2 cup cream and 1 teaspoon sugar until firm peaks form; gently fold the whipped cream into the cherry jam until just combined and streaky. Serve the pots de creme chilled, topped with a dollop of cherry whipped cream.