In a large measuring cup, combine oil, buttermilk, and mashed sweet potato. Add to the dry ingredients and mix until just combined. Transfer dough to a floured work surface. Dip a sharp knife in flour, then cut the dough into thirds lengthwise. Then cut each long strip into 6 equal pieces, making 18 squares in all.
Transfer biscuits to prepared baking sheet.
Bake about 12 to 13 minutes, until tops are golden and firm to the touch. In a large bowl, whisk together pumpkin puree, brown sugar substitute, granulated sugar, egg substitute, cinnamon, ginger, and nutmeg. Gradually add evaporated skim milk, whisking thoroughly. Pour pumpkin mixture into pie shell. Bake for 15 minutes.