Preheat the oven to 375°F. Coat a 9" pie pan with cooking spray.

Poke the sweet potatoes with a fork in several places. Set on a baking sheet and roast until tender, 45 to 50 minutes. Allow to cool for 15 minutes. Halve and scoop out the potato with a spoon, discarding the skin. Transfer the potato to a bowl and mash until smooth.

Reduce the oven to 350°F. In the bowl of a food processor, place the graham crackers, flaxseed, and 2 tablespoons of the sugar. Process into coarse crumbs and transfer to a bowl. Melt 2 tablespoons of the butter and pour into the crumb mixture; mix until well combined. Pour into the prepared pie dish and press into the bottom and up the sides. Bake for 8 minutes, or until lightly browned. Cool.

Meanwhile, in a large bowl, combine the potatoes, 1/2 cup of the sugar, the milk, eggs, egg white, 2 tablespoons of the flour, vanilla extract, cinnamon, and ginger and whisk until smooth. Pour into the cooled crust and bake for 25 minutes.

While the pie bakes, in a small bowl, combine the remaining 1/4 cup sugar, 2 tablespoons flour, oats, and pecan halves. Add the remaining 3 tablespoons butter and rub in with your fingertips until the mixture holds clumps when pressed. Remove the pie from the oven and sprinkle the top with the oat mixture. Return to the oven and bake until the filling is set and the top is browned, 18 to 20 minutes. Cool for 30 minutes before slicing. Serves 16.