Preheat the oven to 375°F. Line a baking sheet with parchment or foil.
Use a sharp knife to pierce the sweet potatoes 3-4 times. Place on baking sheet. Bake for 60-70 minutes or until fork tender. Lower the oven temperature to 350°F.
Allow sweet potatoes to rest until cool enough to handle. Use a spoon to remove from skin.
Add sweet potato flesh to a medium-size mixing bowl with the evaporated milk, brown sugar, melted butter, eggs, pumpkin pie spice and salt. Using an electric mixer, whip until smooth.
Spray a 2 quart casserole dish with cooking spray. Spread whipped filling evenly into dish.
To make streusel topping: In a small mixing bowl mix together the flour, brown sugar, pumpkin pie spice and salt. Using a pastry blender or 2 forks, cut butter into crumbs until it resembles peas. Stir in the pecans. Sprinkle on top of filling.
Bake in 350°F oven for 45-55 minutes or until the topping is golden and sweet potatoes are set when gently shaken. Serve warm.