Limoncello Gelato

2 c. heavy whipping cream

1/2 c. whole milk

1/4 c. buttermilk

1/4 c. mascarpone cheese

4 coffee beans

1 tsp. finely grated lemon peel

1 vanilla bean

4 large egg yolks

1/2 c. sugar

2 T. fresh lemon juice

1/4 c. limoncello plus additional for serving

Whisk the first 6 ingredients in a large saucepan.  Split the vanilla bean lengthwise then scrape the seeds from the bean.  Put both the bean and the seeds in the saucepan also.  Cook over medium-high heat until bubbles form at the edges, stirring occasionally.  Remove from heat, cover and let steep for 15 minutes.

Whisk egg yolks, sugar and lemon juice in a large bowl until thick and smooth.  Strain the cream mixture from the saucepan into a medium bowl.  Slowly whisk the warm cream mixture into the yolk mixture.  Return the combined mixture into the same saucepan.  Stir over medium heat until the custard thickens enough to register 180 degrees (about 6 minutes); do not boil.  Pour the custard into a medium bowl.  Stir in 1/4 cup of limoncello.  Chill the custard until cold, at least 4 hours.  (This can be done a day ahead.  Cover and keep chilled.)

Process the custard in an ice cream maker according to instructions.  Transfer to a container; cover and freeze up to 2 days.

Scoop gelato into glasses.  Drizzle with additional limoncello and serve.