4 tablespoons (1/2 stick) unsalted butter, plus more for coating the slow cooker
1 pound fresh or frozen corn kernels (from about 5 to 6 ears fresh corn, about 3 1/2 cups)
4 large eggs
1 1/3 cups whole milk
2/3 cup heavy cream
1/4 cup all-purpose flour
2 tablespoons granulated sugar
1 teaspoon fine salt
Coat the insert of a 4-quart or larger slow cooker with butter. Melt the 4 tablespoons of butter in a large frying pan over medium heat. Add the corn and cook, stirring occasionally, until any liquid has almost evaporated, about 5 minutes.
Meanwhile, whisk the eggs, milk, cream, flour, sugar, and salt together in a large bowl until combined; set aside.
When the corn is ready, add it to the egg mixture and stir with a rubber spatula to combine. Scrape the mixture into the slow cooker and spread into an even layer.
Cover the slow cooker and cook until the pudding is just set, 2 to 3 hours on LOW depending on the size of the slow cooker. Start checking at 2 hours; the pudding is done when the middle is not liquid anymore, but wobbles gently like Jell-O. Serve immediately.