1. Grease a 6-quart slow cooker and sprinkle with 1/4 cup Parmesan.
2. Melt butter in a large pot over medium heat. Add onion and 1 tablespoon salt and cook until softened, 8 to 10 minutes. Stir in corn, flour, sage, garlic, and pepper, and cook for 1 minute.
3. Slowly whisk in milk, bring to a simmer, and stir frequently until mixture thickens, 5 minutes. Remove from heat, and stir in cheddar, 1/2 cup Parmesan, and 1/2 cup parsley. Let cool 5 minutes before stirring in egg yolks.
4. In a large bowl, beat egg whites with an electric mixer on low until frothy. Increase speed to medium-high and beat until stiff peaks form, about 3 minutes. Stir 1/2 cup egg whites into corn mixture, then use a rubber spatula to fold in remaining whites.
5. Pour into the prepared slow cooker and drape a kitchen towel over the top. Cover and cook on high for 2 hours, rotating crock halfway through. Before serving, sprinkle with remaining 1/4 cup parsley and 1/4 cup Parmesan.
Source: Hannaford fresh Magazine, November - December 2015