How to Make It
In a medium saucepan, combine the milk and the heavy cream with 3/4 cup of the sugar. Add the lemon zest and broken cinnamon stick and bring to a simmer. Cover and let the milk mixture stand off the heat for 30 minutes.
Strain the milk mixture into a bowl. Set the bowl in an ice water bath and stir occasionally until chilled. Pour the milk mixture into a 9-by-13-inch glass dish.
In a large bowl, using an electric mixer, beat the egg whites with the remaining 2 tablespoons of sugar and the lemon juice at high speed until soft peaks form. Dollop the beaten whites all over the milk mixture and freeze until solid, about 5 hours.
Cut the ice milk into 2-inch squares. Using a sturdy spatula, transfer half of the squares to a food processor. Process until completely smooth, scraping down the sides of the bowl. Scrape the smooth ice milk into a bowl and freeze. Repeat with the remaining squares of ice milk. Freeze the ice milk until it is firm but not solid, about 30 minutes.
Scoop the ice milk into 6 tall glasses and top with the chilled espresso. Dollop the drinks with whipped cream and sprinkle with cinnamon. Serve the drinks with straws and long spoons.