A day in advance, make crème fraiche. Make and blind-bake a pastry crust. Cool crust a few minutes and, while the crust is still hot, brush the inside of the pie shell with a thin clear sheen of egg white. If any solidifies and turns white, quickly wipe it away with a paper towel. Set aside. Sort and clean 4 c of blueberries. Place 3 cups of the blueberries in a mixing bowl and set aside. Place the remaining cup of blueberries in a saucepan with 1/2 cup water and bring to boil. Simmer 3-4 minutes. Measure remaining ingredients out. In a separate bowl, mix cornstarch and water until smooth. Add the cornstarch slurry, sugar, and lemon juice to the sauce and stir until the starchy cloudiness goes and sauce thickens to a shiny blue-black. (1 minute.) Pour the hot sauce over the fresh blueberries in bowl and stir gently until all blueberries are coated. Pour blueberries into pie shell and let the pie set up for 2 hours at room temperature. Lasts 2 days at room temperature but is best the day it’s made. Serve with crème fraîche.