How to Make It
In a medium saucepan, bring the cream to a simmer. Remove from the heat. Add both chocolates and let stand until melted, about 2 minutes. Whisk vigorously until smooth, then stir in the bourbon. Pour the crémeux into 8 glasses. Refrigerate until chilled, at least 1 hour.
In a medium saucepan, toast the sesame seeds over moderate heat, shaking the pan, until golden, 1 to 2 minutes. Remove from the heat and let cool slightly. Add the milk, cover and let steep for 30 minutes.
Set a heatproof bowl in a bowl of ice water. Transfer the sesame milk to a blender and pulse several times, until the seeds are chopped but not ground. Rinse out the saucepan and strain the milk into it, pressing hard on the solids to extract as much milk as possible. Return the milk to a simmer.
In a medium bowl, whisk the yolks with the sugar until pale. Whisk in 1/2 cup of the hot milk, then whisk the mixture into the saucepan. Cook over moderate heat, whisking, until thickened, about 5 minutes. Pour the crème anglaise into the bowl set over ice water and let cool completely, stirring occasionally.
To serve, gently pour the chilled crème anglaise over the crémeux. Sprinkle with black sesame seeds, lime zest and fleur de sel. Serve right away.