Preheat the oven to 400°F.

Poke the potatoes a few times with a fork. Roast them for 50-60 minutes or until they are soft when pierced with a fork. Allow them to cool to room temperature on the baking sheet.

Once they are cooled, peel and discard the skin. Mash the potato flesh with a fork until smooth. If you don't like the bits of sweet potato in your biscuits, purée the potatoes until smooth.

In a small bowl, combine the yogurt, milk and sweet potatoes.

In a large bowl, combine the flour, baking powder, sugar, cinnamon and salt. With a pastry cutter, cut in the butter until they are the size of peas.

Stir in the milk mixture with a spoon until the dough starts to come together. Then knead in the bowl with your hand until just combined. You don't want to warm the dough by messing too much.

Roll the dough out onto a lightly floured surface and flatten to 1 inch thickness. Using a 2 inch circle biscuit cutter, cut the biscuits by going straight up and down on the dough (don't twist).

Place the biscuits on a silpat or parchment paper covered baking sheet and bake for 10-14 minutes, or until slightly golden on top. Cool on a cooling rack or enjoy warm.

(Optional) Cut a biscuit in half, line each half with marshmallows and broil for a few seconds until puffy and browned.