Microwave chocolate at HIGH 1 ½ minutes or until melted, stirring twice; stir in brewed coffee. Set chocolate mixture aside.
Beat yolks and ¼ cup sugar at high speed with an electric mixer until thick and pale. Put aside.
Bring whipping cream, half-and-half, remaining ½ cup sugar, and coffee granules to a boil in a heavy saucepan over medium-high heat, stirring until sugar and coffee dissolve.
With mixer at low speed, gradually pour hot cream mixture into yolk mixture; return to saucepan. Cook over medium heat, stirring constantly, 6 - 8 minutes or until mixture thickens and coats a wooden spoon. Remove from heat.
Stir in chocolate mixture, cover and chill 2 hours.
Transfer the mixture into an ice cream machine and churn until frozen, 15-30 minutes, according to the manufacturer’s instructions.
Transfer to plastic container and place in the freezer for an hour before serving.