Set up an ice bath using a large bowl filled with ice and a little water. Set a slightly smaller bowl in the ice bath, pour 1 cup of the heavy cream into that bowl and set a fine-mesh strainer atop.
In a saucepan, add the 1/2 cup of cream, the milk, and pinch of salt. Turn the heat to medium-low.
Once the milk and cream have warmed and is steaming but not boiling, whisk the eggs and egg yolk with the sugar in a medium sized bowl until pale yellow.
Drizzle the heated milk/cream into the egg/sugar mix very slowly while constantly whisking to temper the eggs. Once the egg mix has warmed, add it back to the saucepan. Turn the heat to about medium and whisk until the custard thickens and coats the back of a spoon.
Remove the ice cream base from the heat, pour it through the strainer into the reserved cream. Add the vanilla, stir, cover the liquid with plastic wrap directly on the surface, and let cool completely. The whole ice bath can be set in the refrigerator to speed the process.
In the meantime, make the crisp by preheating the oven to 375° F (190° C). Once the oven is heated, mix all the crisp ingredients in a small bowl. Line a cookie sheet with parchment paper, a silicone mat, or lightly spray it with cooking spray then spread out the crisp mix onto it. Break up any larger clumps.
Bake the crisp for about 10 minutes. Remove the sheet from the oven and cook completely.
When ready to churn, add the apple butter to the ice cream base, stir it in thoroughly, then add the mix to the ice cream maker. Churn as directed by the manufacturer’s instructions.
Layer the ice cream in a freezer-safe container with the crisp, cover, and transfer to the freezer to set firm. Serve as is, with any leftover crisp atop if there is any, a caramel sauce, whipped cream, or as desired.