1. Put cream and milk into a medium saucepan over medium-high heat. Heat the mixture until hot (do not let simmer), about 2 minutes. Remove mixture from heat; cover, and let stand 30 minutes.
将奶油和牛奶混合放在适温的锅里，加热大约2分钟（不要沸腾），移离火源，封盖存放30分钟。
2. Prepare an ice-water bath; set aside. Put yolks, sugar, and salt into the bowl of an electric mixer fitted with the whisk attachment. Beat on high speed until yolk mixture has tripled in volume and can hold a ribbon on surface for 2 seconds, about 3 minutes.
3. Reduce speed to medium. Ladle 1 cup cream mixture in a slow stream into yolk mixture to temper it. Add another cup cream mixture; beat to combine. Transfer mixture to saucepan; cook over medium-high heat, stirring constantly, until it is thick enough to coat the back of a wooden spoon and an instant-read thermometer registers 180°, 5 to 7 minutes. Stir bittersweet and milk chocolates into custard.
温度降到中等，取一勺奶油缓缓倒入混合物中再回火，再加一勺奶油混合在一起，然后放入锅内，加到中高温直至它浓到能粘住木勺，立即保持温度在180度5到7分钟然后将咖啡和牛奶巧克力加进去．
4. Pour custard through a medium-mesh sieve into a bowl set in ice-water bath. Let cool completely, stirring often.
通过中筛网把奶油冻倒入冰水盆内的碗中．让它完全冷却，这常常时最为激动人心的时刻了．
5. Freeze custard in an ice cream maker according to manufacturer's instructions. Serve immediately, or freeze in an airtight plastic container until ready to serve. If frozen for more than 4 hours, let ice cream stand at room temperature 15 to 20 minutes before serving.
放在制冰机中冷却奶油时，一定要厂家的说明去做．一旦冻好，立即供应，否则要冷藏在一个密封的塑料桶里．如果冷冻超过4小时，必须取出置于常温下15到20分钟，方可食用．
