Step 1
Toast sesame seeds in a dry large skillet over medium heat, stirring often, until fragrant and just starting to crackle, about 2 minutes. Transfer to a food processor or blender and pulse, scraping down sides as needed, until seeds are finely chopped but haven’t formed a paste, about 3 minutes in a food processor, and about 2 minutes in a blender.
Step 2
Mix together ground sesame seeds, condensed milk, and salt in a medium bowl.
Step 3
Using an electric mixer, beat cream in a small bowl, starting on low speed and gradually increasing to medium-high as it thickens, until billowy and stiff peaks form, about 5 minutes.
Step 4
Add a dollop of whipped cream to condensed milk mixture and mix in with a rubber spatula (this is just to lighten it so that the next stage—folding—is easier). Add remaining whipped cream and fold in, running spatula down sides and along bottom of bowl and lifting up through center and over top while rotating bowl to integrate without deflating, until very few streaks of condensed milk mixture remain. Fold in crushed cookies; scrape ice cream base into a loaf pan that’s at least 8½x4½”. Cover with plastic wrap or an airtight silicone lid and freeze until solid, at least 8 hours.
Step 5
To serve, transfer loaf pan to refrigerator and let ice cream soften 10 minutes before scooping into bowls.
Step 6
Do ahead: Ice cream can be made 1 week ahead. Keep frozen.
