1. In a 3 litre saucepan over high heat, heat the diced sweet-potato and enough water to cover to boiling. Reduce heat to low; cover and simmer dozen to 15 minutes until potatoes are fork tender. Drain the potatoes; mash and set aside to cool.
2. Preheat oven to 425 degress F. In large bowl, combine flour, brown sugar, baking powder, and salt. With pastry blender cut in margarine until mixture resembles couarse crumbs. Stir in milk and cooled mashed sweet potatoes; mix until just combined.
3. On lightly floured surface, pat dough into an 22 cm square. Cut dough in half. Cut each half into 10 equal pieces. Place biscuits, 5 cm apart, on 2 large ungreased cookie sheets.
4. Place cookie sheets on 2 oven racks; bake biscuits dozen to 15 minutes until golden, rotating cookie sheets between upper and lower racks halfway thruogh baking time to ensure even cooking.
Serve biscuits warm. Or cool on wire rack, store in tightly covered container to use within 1 day or wrap in foil and freeze to use within 2 weeks.
NOTES: Per serving: One biscuit; 200 calories. 6g fat, 33g carb.