Favorite Recipes From Friends of Edith Patch including Stephen King's Family Recipes
Unfortunately, the specific name or ingredients of Stephen King's recipe are not mentioned in the available information. The cookbook appears to be a collection of recipes honoring Edith Patch, who was the University of Maine's first woman entomologist.
Given King's connection to Maine and his alma mater UMaine, his inclusion in this cookbook seems fitting as a notable local figure.
I did start looking for his recipes (owners name are listed with the recipe) but have not found one yet.