Put oatmeal in food processor and pulse until a flour-like consistency.
Add regular and whole wheat flour, baking powder, baking soda, salt, ginger & cinnamon to the ground oat flour. Pulse to mix.
In another bowl, beat egg. Then add vanilla, oil, brown sugar and evaporated milk, whisk to blend.
Add the flour mixture to the wet ingredients and mix well.
Add the sweet potato and stir in, until evenly distributed.
Spoon batter into baking liners or directly into greased muffin tin. Fill nearly full.
In a small bowl mix the topping ingredients. Sprinkle generously on the muffins, you should have the right amount for about a dozen standard size muffins.