Preheat the oven to 425 degrees F and line a baking sheet w/ parchment paper. Set aside.
In a medium bowl, mash together the sweet potato, maple syrup, and 3 tablespoons of the milk until well combined. Set aside.
In a separate bowl, combine flour, baking powder, salt, pumpkin pie spice, cinnamon, and brown sugar and whisk until well incorporated. Using a box grater, grate the butter into the flour mixture then, using clean hands, gently blend the butter bits into the flour until it's the size of small peas.
Add the sweet potato mixture to the flour mixture and gently mix until combined. Drizzle in the additional milk, one tablespoon at a time, until the dough is just moistened and holds together. You may need some of it, all of it, or none of it at all.
Sprinkle countertop or work surface with flour and dump out the dough. Knead the dough 2-3 times until it comes together. Roll the dough into a 8" circle. Fold in half and then fold in half again. Lightly roll the dough into another 8" circle. Fold in half and then fold in half again. Lightly roll out the dough one last time to 1/2" to 3/4" thickness
Using a 2" round biscuit cutter or a lightly floured glass, cut out biscuits by pressing down into the dough and pulling straight up. Do not twist the cutter at all. Reform leftover dough to cut the remaining biscuits.
Add the biscuits to the prepared baking sheet, a few inches apart, and bake for 12-14 minutes or until the bottoms are lightly golden and the biscuits are firm and cooked through.
Grab & Go Breakfast: These sweet potato biscuits are perfect for freezing for a quick grab-and-go breakfast! Cook and cool completely then wrap individually and place in a freezer bag for quick meals on the go. To reheat, place a biscuit in a damp paper towel and microwave on medium setting for 45 seconds to 1 minute until warm. Stuff with your favorite fillings and serve!