Preheat oven. 180 degrees C/350 degrees C for Fan oven.
Fill a medium size saucepan with water and heat on high. Peel and chop the sweet potato and place in the saucepan with a lid. Bring to the boil. Reduce heat and cook until sweet potato becomes soft (use a fork to poke – if soft remove from heat)
Drain the sweet potato and use a fork to mask it up, ensuring all lumps are removed. Set aside to cool.
In a medium sized mixing bowl, add the oat flour, cocoa powder, granulated stevia, cream of tartar and bicarb soda. Mix to combine
Melt the peanut butter in a microwave save jug for 1 minute. Add to the dry ingredients. Do not stir in.
Add the 2 eggs to the bowl and use a spatula to fold in the wet ingredients to the dry ingredients to form a pasty batter.
Once cooled, add the mashed sweet potato and stir in with a spoon until a thick batter is formed.
Lightly spray the silicone muffin trays with oil and spoon the batter across 8 molds, going halfway up in each mold.
Cook muffins for 18 to 20 minutes. Check with a cake skewer before removing to ensure they are cooked.
Leave for 10 to 15 minutes to cool before removing from trays.
Store in an air tight container at room temperature for up to 4 days. Or freeze for up to 4 weeks