Place a one quart container in the freezer to chill.
In a medium sauce pan, whisk together lime zest and sugar until fragrant. Whisk in lime juice, eggs, and milk to combine.
Warm the mixture over medium heat, whisking constantly until steam rises from the pan and it begins to bubble around the edges.
Using a fine mesh sieve, strain the custard into a one quart spouted measuring cup, pressing to extract the juices from the zest. Whisk in vanilla and heavy cream. Cover and chill until until the mixture is cold.
Freeze the lime ice cream base according to the instructions of your ice cream mixer.
Once the ice cream is ready, spoon it into the pre-frozen container. Cover and place the ice cream in the freezer for several hours.
If desired, top scoops of ice cream with crushed graham cracker and edible flowers or fresh mint leaves before serving.