The Smoothest Ice Cream Is Made with Liquid Nitrogen
Robyn Sue Fisher, founder of San Francisco’s innovative churned-to-order ice cream shop, Smitten Ice Cream, invented the true cop’s delight: coffee and doughnuts ice cream. She starts making ice cream from scratch with a base of heavy cream, salt, sugar, and coffee grounds whisked together in a large pot. She lets the coffee steep in cream for 10 minutes over medium heat and then strains the mixture to remove the coffee grounds. (Note: Fisher only uses the best products in her ice cream, and swears Blue Bottle is the crème de la crème.) After the heavy cream mixture cools, you can place it in an ice cream machine at home, but Fisher flash-freezes the liquid in a machine she designed herself using liquid nitrogen.
A self-proclaimed science nerd, Fisher spent two years in a basement workshop with a retired engineer inventing Smitten’s now-patented ice cream machine, which she calls Brrr. Seeking to learn more about ice crystal formation, she found that the colder you freeze ice cream, the smaller the ice crystals are. And the smaller the ice crystals are, the smoother the product. This realization led her to liquid nitrogen, which freezes at a temperature of -321°F. Her machine uses liquid nitrogen to freeze ice cream in less than 30 seconds.
During the Great Recession, in 2009, Fisher began selling ice cream from a rickety red wagon in San Francisco. She let her fans know where to find her using Twitter, and usually ended her tweets with “Come and get it before it sells out—or before the cops come.” Now that she’s outgrown her wagon and settled into seven storefronts on the West Coast, she serves up a cop’s breakfast in ice cream form with coffee and doughnuts. Ice cream for breakfast? We’re on our way.
Coffee & Doughnuts Ice Cream
How to Make It
Combine ground coffee, salt, and sugar in large pot. Whisk to combine thoroughly, then whisk in half-and-half and first amount of heavy cream, making sure no coffee grounds are left clinging to side of pot.
Bring mixture to simmer (small bubbles begin to form around edges of pot) over medium high heat, stirring occasionally. Watch carefully—do not let it boil over. Once at a simmer, remove from heat.
Off heat, cover, and steep for EXACTLY 10 minutes. Set a timer.
Slowly pour the mixture through a fine strainer (or chinois) over a large bowl or pot. Press on the grounds with medium pressure using a wooden spoon or ladle to extract the liquid. Do not press too hard, or try to get every last drop of liquid through, as this will make the base taste bitter.
Add vanilla and instant espresso powder to mixture. Whisk or mix using an immersion blender until thoroughly combined. Chill until cool.
To make the ice cream base, combine milk, second amount of heavy cream, and second amount of sugar. Heat over medium heat, stirring regularly, until the mixture reaches a simmer. Remove from heat.
Place bowl over an ice bath (a large container or bowl filled with ice and just enough water for the ice to move around freely) and stir occasionally until cool.
Whisk ice cream base into second coffee mixture.
Freeze combined base according to your ice cream maker’s instructions.
While ice cream is still soft, fold in pieces of donuts. Do not overmix.
Let freeze until solid.
