Espresso Gelati Sundaes

In a heavy medium saucepan, combine the cream, milk, half-and-half, lemon zest and 1/4 cup of the sugar. Bring to a simmer over moderate heat, stirring occasionally.

Meanwhile, in a bowl, whisk the egg yolks with the remaining 3/4 cup of sugar. Whisk in the hot cream mixture and return the custard to the saucepan. Cook for 6 minutes, stirring constantly; do not let it boil. Strain into a bowl and stir in the corn syrup and vanilla. Refrigerate until chilled. Working in 2 batches, freeze the custard in an ice cream maker according to the manufacturer's instructions. Transfer to a chilled bowl and store in the freezer.

In a heavy large saucepan, combine the sugar, cocoa, 1/2 cup of the corn syrup and 5 cups of water. Bring to a boil over moderately high heat and cook, stirring often, until the syrup is very thick and reduced to 3 1/4 cups, about 40 minutes.

Scrape the syrup into a bowl, stir in the remaining 1/2 cup of corn syrup and the cream. Refrigerate until chilled. Working in 2 batches, freeze the mixture in an ice cream maker according to the manufacturer's instructions. Transfer to a chilled bowl and store in the freezer.

Place 1 to 2 scoops of the chocolate gelato into parfait glasses and add a scoop or two of the cream gelato. Drizzle with 1 to 2 tablespoons of espresso and serve.