Biscuit Experiment 02: Sweet Potato Biscuits

I wasn't going to post this recipe because I was totally unimpressed. I know, I know, sweet potato biscuits have to be delicious, right?
I'm not saying they weren't good, they just didn't meet my standards. I want some lift, some fluffiness! And these didn't do it for me.

The reason I attempted this recipe was for a several reasons.
1. Sweet potatoes. yum.
2. The recipe required the butter to be frozen and then grated through a box grater. I thought this was an interesting twist to simply chilling the butter and then cutting into cubes. I wanted to see if this technique made any difference in the quality of the biscuits. It did not, as far as I could tell.
3. This recipe did NOT call for the piercing of the dough as the previous biscuit recipe did (Scott Peacock's recipe). I wanted to know if not perforating the dough would have an effect on the lightness of the biscuits. These biscuits were flat and didn't rise very much, but whether the perforation had anything to do with it, I have no idea.
In addition, I read a tip that said you should sift the flour on its own and then sift again with the other dry ingredients for more lift. Well, that didn't work.

I am wondering if I hadn't added the sweet potato, what kind of biscuit would this be?

This is my Great Biscuit Experiment and I definitely learned something from cooking these biscuits. But will I make these again? Nope.

Sweet Potato Biscuits featured on Chow.com by Kate Ramos

INGREDIENTS
2 cups all-purpose flour
1 tablespoon baking powder
1 tablespoon granulated sugar
1/2 teaspoon kosher salt
1/4 teaspoon baking soda
3/4 cup whole milk
1 cup baked, mashed sweet potato about 1 medium potato
8 tablespoons unsalted butter 1 stick, frozen
Heavy cream for brushing the tops

INSTRUCTIONS
1.  Heat the oven to 400°F and arrange a rack in the middle. Combine all dry ingredients in a large
mixing bowl and set aside. In a separate large bowl, mix together milk and mashed sweet potato
until evenly combined.

2.  Grate frozen butter through the large holes of a box grater and toss with dry ingredients until
butter is coated. Add milk mixture and mix lightly until dough forms a shaggy mass.

3.  Turn out mixture onto a floured surface and knead just until it comes together. (The dough will not
be smooth.)

4.  Pat into a circle and use a floured rolling pin to roll dough to a thickness of about 3/4 inch.
Using a 4-inch biscuit cutter, cookie cutter, or glass, cut the dough into rounds. Gather leftover
dough into a circle, reroll, and cut until you have 8 large biscuits.

5.  Place biscuits on a baking sheet, brush tops with heavy cream, and bake until golden, about 12 to
15 minutes.