Preheat the oven to 350 degrees F. Line a loaf pan with parchment such that the parchment strip is hanging over the edge (see pics). Make the Crust: Add all the ingredients except oil in a bowl and mix well. Add 2 tbsp of oil and mix in with a spoon or your hand. Add more oil a tsp at a time to mix in until the crust starts to stick to make fat crumbs.
Transfer mixture to the loaf pan (a stoneware or glass pan works better to keep the crust more shortbread like and reduce overbrowning). Press it down to form a well packed and even crust. Bake for 8 to 10 mins.
Mix everything under the sweet potato layer until well combined. Pour over the baked crust. Bake for 35 to 45 minutes until the top is well set.
Let it cool for 15 minutes, then gently remove from the pan. Chill for atleast an hour before slicing. Longer chilling time (a few hours) makes for a better set top and much more spiced and buttery flavor profile. Serve as is or with a dollop of vegan vanilla ice cream or whipped coconut cream and a dusting of pumpkin pie spice.
Use pumpkin puree for pumpkin pie bars.Tip: Measure out a scant 1/4 cup oil in a 1/4 cup measure to use to make the crust and use the remaining in the sweet potato layer. Use the same 1/4 cup measure for maple syrup, less sticky messTo make Sweet Potato Pie: Double the recipe with double the crust and the filling. Use 3 tbsp starch in the filling and add 10 to 15 minutes to the bake time. Nutrition is for 1 of 8 bars.