How to Make It
Preheat oven to 375°. Spray a 12-cup muffin pan with nonstick baking spray. In the bowl of a large food processor, combine both flours with the oats, sugar, baking powder, salt and ginger. Pulse for 10 seconds. Add the pumpkin puree, marmalade, buttermilk, vinegar and vanilla and pulse several times to combine. Scrape down the side of the bowl. Add the oil, butter and eggs and process until fully incorporated, about 10 seconds.
In a small bowl, mix the oats with the sugar and butter.
Fill the prepared pan with heaping 3-tablespoon-size scoops of batter. Sprinkle on the oat topping. Bake in the center of the oven for about 20 minutes, until a toothpick inserted in the center of a muffin comes out clean. Let the muffins cool in the pan for 5 minutes, then turn them out onto a rack to cool completely. Serve the muffins slightly warm or at room temperature.