In the town of Soriano, especially in autumn, Chestnuts are in everything you eat, ravioli with chestnuts, soup with chestnuts, so why not gelato, too. This is Italy, after all.
IF USING WHOLE COOKED CHESTNUTS, PUREE THEM IN A BLENDER WITH SOME OF THE MILK AND CREAM THEN CONTINUE TO STEP 2
Coarsly chop 2 oz cooked chestnuts, place in a bowl and cover with chestnut liqueur
In a medium saucepan, pour the milk, 8 oz of the cream, the chestnut puree' and the vanilla. Bring to a boil
In a large bowl, whisk egg yolks and sugar together
Pour some of boiling milk into the egg yolk/sugar/chestnut mixture, whisking vigorously so that the hot milk does not cook the eggs
Pour mixture through a sieve, back into the saucepan
Return to medium-low heat and stir continuously till the mixture thickens a bit.
Remove from heat
Add remaining 4 oz cream and the rum
Chill in refrigerator.
Freeze in gelato machine when mixture is cold
When mixture is almost finished freezing, add the chopped drunken chestnuts and allow them to be mixed into the gelato.
Serve immediately, or return to freezer.