Whisk together the heavy cream, whole milk, sugar and molasses in a saucepan. Add the ginger. Bring to a simmer over medium heat. Continue to whisk periodically to help dissolve the sugar. Once it simmers, turn off heat. Do not bring to a boil as this can cause the milk to separate.
Whisk egg yolks, vanilla, cinnamon, allspice, cloves and salt constantly for about three minutes. Add about ¼ to ½ cup of the warm cream mixture into the egg mixture, whisking constantly. This tempers the eggs to gently cook. Repeat this a few times.
Add tempered egg-cream mixture back to the saucepan with the rest of the cream. Whisk constantly over medium heat and bring back to a simmer. Again, do not boil. Cook until mixture thickens and covers the back of a wooden spoon, about six to 10 minutes. Turn off heat and stir in orange zest. Allow to steep for about 10 minutes, stirring occasionally to prevent a film from forming.
Pour the mixture over a fine-mesh sieve into a large mixing bowl and place plastic wrap directly on top of the custard's surface. Refrigerate until cold, at least four hours to ensure proper churning, though I like to chill overnight to really make sure it's cold.
Pour custard into an ice cream maker and churn according to manufacturer’s directors. In the last couple minutes of churning, add the crushed ginger snaps. Pour into an airtight container and freeze for a few hours. Enjoy!