Step 1

Whisk the cream, milk, sugar, vanilla and 1/2 teaspoon salt in a medium saucepan and bring to a simmer over medium heat. Beat the egg yolks in a medium bowl. Slowly whisk 1 cup of the hot cream mixture into the beaten yolks, then pour back into the saucepan, whisking, and return to medium heat. Cook, stirring constantly with a wooden spoon, until the mixture thickens, coats the spoon and reaches 180 degrees F on a thermometer, 6 to 8 minutes. Remove from the heat and strain the custard through a fine-mesh sieve into a large bowl or measuring cup; discard the solids. Stir often until the mixture cools to room temperature. Lightly press plastic wrap directly against the surface of the custard to prevent a skin from forming. Chill until cold, about 3 hours. (For faster chilling, set the bowl of custard in a bowl of ice water and stir until cold.)

Step 2

Place an 8-inch square metal pan in the freezer to chill then freeze the cold custard in an ice cream maker according to the manufacturer's directions. Put the cookies into a resealable plastic bag and lightly crush with the smooth side of a meat mallet or the bottom of a measuring cup.

Step 3

Remove chilled pan and sprinkle in half of the crumbled cookies. Top with half of the ice cream, then repeat with remaining cookies and ice cream. Working quickly, use a spoon to incorporate the cookies into the ice cream mixing from bottom to the top. Cover with plastic wrap and freeze until firm, 2 to 3 hours.