Step 1

Combine the gelatin, sugar and boiling water in a large heatproof bowl; whisk until the sugar and gelatin are dissolved, about 2 minutes. Add the milk and whisk to combine. Cover the bowl and refrigerate until completely cold and the gelatin just starts to set, about 1 hour. (It should not be completely set and firm so you can easily and thoroughly fold in the cream mixture).

Step 2

Whip the heavy cream and the vanilla with a handheld mixer in a medium bowl until stiff peaks form, about 3 minutes. Remove the chilled gelatin mixture from the refrigerator and fold in half of the whipped cream. Add the remaining whipped cream and fold until fully incorporated. Pour into a 2-quart storage container or an 8-by-8-inch baking pan. Cover tightly and freeze for at least 4 hours, up to overnight. Scoop and serve.