Bring a large pot of water to a boil. Add sweet potatoes and cook until tender but still firm, about 30 minutes. Drain, cool, peel and mash. Preheat oven to 350 degrees F (175 degrees C).
In a large bowl, combine sweet potatoes, butter, sugar, vanilla and nutmeg. In a small bowl, whisk together the eggs and milk and blend into the sweet potato mixture.
Pour into pie shells and bake in preheated oven for 60 minutes, or until done.
