Mix all dry ingredients for the muffins in a bowl and set aside
In a seperate bowl, mix all wet ingredients for the muffins and set aside
In a small bowl, mix all ingredients for the streusel topping and set aside
Puree refreshed and drained or baked sweet potatoes until smooth. Measure out 1 1/3 cups. Mix wet muffin ingredients with the pureed sweet potatoes, then slowly mix in the dry ingredients, folding to ensure all mixture is incorporated.
Spoon batter into muffin cups evenly, then spoon streusel topping evenly among cups on top of muffin batter. Bake at 425F for 5 minutes, then turn oven temperature down to 350 for 18 minutes. Check muffins with a toothpick to insure they are cooked completely.
Remove muffins from pan and let cool on a baking rack. If you cant consume within 3 days, you can refrigerate for 7.