Preheat oven to 350°F/175°C. Line muffin pans with muffin/cupcake liners. Makes about 16 regular-size muffins.
In a small bowl mix the topping ingredients. Stir until combined and set aside.
In a medium-sized bowl mix together the flours, oatmeal, baking powder, baking soda, salt, and cinnamon. Set aside.
In a separate medium-sized bowl mix together the pumpkin, ground flax seed, corn starch, plant milk, brown sugar, peanut butter, vegetable oil, and vanilla. Stir together until combined.
Pour the flour mixture into the pumpkin mixture and stir until just combined. Pour the batter into lined muffin tins about 3/4 of the way full. Top each with a teaspoon or two of the topping.
Place muffins in the heated oven and bake for about 20-25 minutes, or until lightly golden on top.
Remove from the oven and allow them to cool slightly. Serve warm.