In a medium saucepan, combine the cream and milk and stir over medium heat until it simmers.
Meanwhiile, in a medium bowl, whisk together the egg yolks, sugar and tahini (try to whisk out the lumps).
Place the chocolate in a separate bowl
When the milk mixture is steamy, pour the hot milk over the chocolate. Let it sit 1 minute, then whisk it slowly until the chocolate is melted and the ganache is smooth, then pour this mixture over the whisked egg mixture to temper them.
Strain the mixture into a large, 4-cup (1 L) measuring cup or a bowl with a spout preferably. Then divide the chocolate custard between 5–6 ramekins.
Place the ramekins in a deep roasting pan and fill the pan with hot water so that it reaches at least halfway up the ramekins.
Bake the custards for 40 minutes or until the centers are completely set. Cool to room temperature, then chill before serving. Topped with a sprinkling of toasted sesame seeds.
Notes
For the milk chocolate, I used Cacao Barry Alunga 41 % milk chocolate.