In a large pot, bring 6 cups water and salt to a boil over medium-high heat. Working in batches, add greens to boiling water. Cook until greens brighten in color, 1 to 2 minutes. Transfer greens to an ice water bath to stop cooking process. Drain; gather blanched greens in cheesecloth or a kitchen towel, and wring out any excess moisture. Transfer to a large bowl.
Heat a 10-inch cast-iron skillet over medium heat. Add bacon, and cook until crisp and browned, about 5 minutes. Add green onion and garlic, and cook, stirring occasionally, until aromatic, 2 to 3 minutes. Stir in cream, and cook for 2 minutes. Let cool slightly; add to greens.
Add feta, parsley, eggs, crushed red pepper, and black pepper to greens, gently stirring until well combined.
Lightly spray a 9-inch pie plate with cooking spray. Lay 1 sheet of phyllo in prepared plate, and gently press to fit. Spray sheet with cooking spray. Lay another sheet on top of first sheet, crisscrossing the 2 sheets; spray with cooking spray. Repeat with remaining sheets of phyllo. Spoon greens mixture into prepared crust. Gently fold phyllo dough around edges.
Bake until crust is golden brown and filling is set, 40 to 45 minutes, covering with foil halfway through baking to prevent excess browning. Garnish with Parmesan, if desired.
Recipe by Louisiana Cookin' at https://louisianacookin.com/fall-greens-pie/