Mocha Custards with Buttermilk Doughnuts

Combine cream, milk, and ground coffee beans in heavy medium saucepan. Scrape seeds from vanilla bean into mixture; add bean. Bring mixture to simmer. Remove from heat; let steep 1 hour. Preheat oven to 350 °F. Strain cream mixture into bowl. Return mixture to saucepan. Add chocolate and stir over low heat until chocolate is melted and smooth. Remove from heat. Stir in Kahlúa. Whisk sugar and egg yolks in large bowl to blend. Gradually whisk in 1/3 of chocolate mixture. Whisk in remaining chocolate mixture. Strain custard into another bowl. Place six 3/4-cup custard cups or ramekins in roasting pan. Divide chocolate mixture among cups. Fill roasting pan with enough hot water to come halfway up sides of cups. Cover pan with foil and bake until custards are set, about 45 minutes. Remove custards from water. Cool, then cover and refrigerate until cold, about 3 hours. (Can be made 1 day ahead. Keep refrigerated.) Serve each custard with 1 buttermilk doughnut.