1. Toast the chile in a small skillet over medium heat, pressing it flat, about 10 seconds per side. Place in a small saucepan with the half-and-half and heat until steaming. Cover and let steep for 10 minutes, then process in a blender until smooth. Strain back into the saucepan.
  2. Reheat the mixture until just steaming. Spread the chocolate into a thin layer in the bottom of a bowl, and pour the cream mixture over it. Stir until the chocolate melts.
  3. In the top of a double-boiler, whisk together the yolks and sugar, then whisk in the chocolate mixture. Place over the simmering water and whisk frequently until it thickens, about 5 minutes (180 degrees).
  4. Cool over ice while whisking regularly.
  5. Stir in the heavy cream, vanilla, and Kahlua, and freeze according to the machine directions.

source: Fiesta at Rick's - Rick Bayless