For the crust:
2 sweet potatoes (about 11 ounces each)
2 cups all-purpose flour
1 teaspoon baking powder
1/2 teaspoon salt
1/3 cup butter
1 – 2 tablespoons buttermilk or milk
For the Filling:
Drizzle a little oil in a baking dish and place the chicken breasts on top. Rub a little oil on top of the chicken and season with salt and pepper. Cover the dish tightly with foil and bake until the chicken reaches 165 degrees F., internal temperature, about 25 minutes. Remove the chicken to a plate to cool completely. When the chicken is cool, cut it into bite-sized chunks.
Dice the bacon into small pieces (I find scissors a great tool for this) and sauté in a large skillet until crispy. Remove the bacon to a paper towel-lined plate with a slotted spoon. Let the bacon grease cool a little, then carefully pour it into a measuring cup and set it aside. Let the skillet cool until it is safe to touch, then wipe out any burned bits or dark brown spots. Return the skillet to medium high heat and pour in two tablespoons bacon grease. Add the diced onion and sauté, stirring frequently, until the onion is soft and translucent, being careful not to burn or brown the onions. Pour in one cup of water, cover the skillet and cook the onions until they are soft and begin to turn a golden color, about 20 minutes. Stir occasionally and add a splash more water to prevent sticking as needed. Remove the lid and cook until all moisture is evaporated and the onions are lightly caramelized.
Add 1 tablespoon of bacon grease and the butter to the onions. Stir well, and when the butter is melted, sprinkle over the flour. Stir everything together until there is no trace of flour visible. Slowly whisk in the milk and chicken broth (measure them together in a four cup measuring jug), scraping the flour from the bottom of the pan. Add the chopped sage, nutmeg, a generous pinch of salt and lots of ground black pepper. Cook over medium-high heat, stirring constantly, until the sauce is thick and coats the back of a spoon, about 10 minutes.