24 hours before you plan to make ice cream, place ice cream maker bowl in freezer to chill. Keep frozen just until custard is ready to freeze.
Place crumbled gingersnaps and 2 cups whole milk in a medium bowl, stir, and set aside to infuse for 1 hour.
While milk infuses, separate 4 egg yolks from whites, placing yolks in a small bowl.
Heat heavy whipping cream over medium flame. Add granulated sugar and pinch of sea salt and stir until dissolved in cream, heating just until sugar and salt are dissolved. Remove from heat and whisk 1/3 cup of cream mixture into yolks, tempering them to add to the hot cream.
Whisking constantly, add yolk mixture into cream mixture, and return to medium-low flame. Continue whisking until a custard forms—it will coat the back of a spoon and gently hold its shape.
Remove from heat and chill completely.
After milk and gingersnaps have infused for an hour, strain through a cheesecloth or fine mesh sieve. Discard gingersnaps, and whisk infused milk into chilled custard. Add bourbon and whisk thoroughly to remove any clumps, or pass through sieve again.
Assemble ice cream maker and freeze custard according to your machine’s instructions. Once frozen, place in freezer proof dish and freeze for at least 3 hours.