Preheat oven to 450 degrees. Prepare baking sheet with parchment paper. Separate 4 Tbsp. butter, cut into 1/4" dice, and put in refrigerator until use. Keep remaining butter out to soften. In a medium mixing bowl, combine 1 1/4 cup flour (reserve the rest for dusting on your workspace), white sugar, baking powder, half the cinnamon, baking soda, and 2 pinches of salt. Mix to combine. In a small bowl, mash sweet potatoes with a fork, add buttermilk, stir to combine, and set aside.

Remove butter from the refrigerator and add to flour mixture. Pinch pieces of butter between your fingers to create smaller pieces of butter; this is called "cutting in." Continue pinching until the mixture looks like wet sand and the butter is the size of small misshapen peas.

Add sweet potato-buttermilk mix to flour-butter mix and stir to combine with a fork until wet ingredients are fully absorbed into dry ingredients. Dust your workstation with some of the remaining flour, enough so dough doesn't stick. Knead dough 4 or 5 times to help bring it together. (Don't overwork the dough: it will cause your biscuits to be tough instead of light and flaky.) Using your hands, pat dough down into a rectangular shape (about 4" x 6") and about 1" thick. This does not have to be perfect.

Cut 4 triangles (or squares if you prefer) and place biscuits on prepared baking sheet. Melt 1 Tbsp. of remaining butter in the microwave or using a small pan and gently brush melted butter over the biscuits. (If you do not have a brush, you can use a spoon, fork, or even your fingers!) Place in oven and bake for approximately 14-16 minutes. When finished, the tops will become golden brown.

While biscuits are baking, in a small bowl, add remaining 3 Tbsp. of softened butter, remaining cinnamon, and brown sugar. Stir to combine.

Remove biscuits from oven and serve warm with the delicious butter. Yum!