½ cup canned pumpkin pie filling (the kind with spices/sugar already in it!)
Pinch fine sea salt
For the corn flake crumble:
3 cups corn flakes cereal
6 tablespoons cold unsalted butter, cut into ¼-inch cubes and slightly softened
1 tablespoon sugar
½ teaspoon fine sea salt
¼ teaspoon ground cinnamon
Make the Pumpkin Pie Custard: Preheat the oven to 325°F. Add the milk, eggs, sugar, pumpkin pie filling, and the pinch of salt to a blender and blend until smooth. Arrange 4 (6-ounce) or 6 (4-ounce) ramekins in a baking or casserole dish (make sure it has sides at least 2 inches high), then distribute the custard mixture evenly among the ramekins, leaving about ¼-inch headroom at the top of each ramekin.
Place the baking dish in the oven and use a pitcher to gently pour warm water into the dish (try not to splash!), watching the water level until it reaches ½-inch from the tops of the ramekins. Bake until slightly jiggly in the center, 50 minutes to 1 hour.
Carefully remove the custards from the oven and take out of the baking dish. Let cool to room temperature, then cover tightly with plastic wrap and refrigerate for at least 3 hours and up to 24 hours.
Make the Corn Flake Crumble: While the custard is cooling, preheat the oven to 300°F. Combine the corn flakes, butter, sugar, salt, and cinnamon in a large bowl and use hands to mix and break up the corn flakes until the mixture resembles granola. Spread the mixture out on a rimmed baking sheet and bake until browned and toasted, 3 to 4 minutes; cool.
To serve, top the cooled custards with the crumble.