Cook the bacon in a skillet until crisp, drain, reserving one and one-half tablespoons of the grease. (Do not skimp and go low fat here; it’s so not worth it). Crumble the bacon.
In a heavy saucepan, cook the onion, leek, garlic and bay leaf with salt and pepper to taste in the reserved grease over medium heat, stirring until softened. Add the squash, apples, broth and one-half cup water. Simmer the mixture, covered, until the squash is tender, about 15 minutes. Discard the bay leaf.
In a blender, puree the mixture in batches, transferring as it is pureed to a clean saucepan. Add enough additional water to thin soup to a desired consistency. Whisk in the sour cream or crème fraiche, season with salt and pepper to taste. Heat soup over medium-low heat until hot (DO NOT BOIL!!!). Serve the soup topped with crumbled bacon and accompaniments. Feel free to double the recipe. I always do.
Makes about 4 1/2 cups