Step 1

Process gingersnaps in a food processor until crumbled, about 30 seconds. Add butter, and pulse until mixture is combined and can hold its shape when pinched, 10 to 15 pulses. Transfer crumb mixture to a 9-inch pie plate; press mixture on bottom and up sides. Transfer to freezer for 1 hour.

Step 2

Beat cream cheese with an electric mixer on medium speed until light and fluffy, about 1 minute, stopping to scrape down sides of bowl with a rubber spatula as needed. Add condensed milk, and beat on medium speed until combined and creamy, about 1 minute. Add lemon zest, lemon juice, and vanilla; beat on low speed until fully incorporated, about 1 minute.

Step 3

Stir together gelatin and water in a small bowl; let stand 2 minutes. Add gelatin mixture to cream cheese mixture. Beat on low speed until fully incorporated, about 1 minute.

Step 4

Remove pie crust from freezer, and pour cream cheese mixture into prepared crust. Transfer to refrigerator, and chill until cream cheese mixture is fully set, about 2 hours. Spread top with whipped cream, and, if desired, garnish with gingersnap crumbs, and lemon peel twists.