Cook and mash the sweet potato until smooth. Measure 1 cup and allow it to cool.
Preheat the oven to 425°F. Line a baking sheet with parchment paper.
In a large bowl, whisk together flour, baking powder, sugar, and salt.
Grate the frozen butter into the flour mixture or cut it into very small pieces. Gently work it into the flour, leaving small pieces of butter visible.
In a separate bowl, combine the mashed sweet potato with the cold buttermilk.
Pour the sweet potato mixture into the dry ingredients and gently stir until a shaggy dough forms.
Turn the dough onto a lightly floured surface.
Gently pat the dough into a rectangle, fold it in half, and gently press it back down. Repeat the folding process several times to create layers.
Pat the dough to approximately ¾–1 inch thick.
Cut biscuits using a biscuit cutter, pressing straight down without twisting.
Place the biscuits on the prepared baking sheet.
Bake until the biscuits are puffed and golden, approximately 15–20 minutes.
While the biscuits bake, combine softened butter, brown sugar, maple syrup, and pumpkin spice. Mix until smooth.
Serve the warm biscuits with maple brown sugar butter.