Preheat oven to 350°F.
In a large mixing bowl, whisk together the flour, ground flax, cocoa powder, sugar, baking soda, salt, and cinnamon.
In medium-sized bowl, stir together the mashed bananas, pumpkin or sweet potato puree, yogurt, eggs, vanilla, honey, and oil until combined.
Add the wet mixture to dry ingredients. Stir just until mixed. Do not over mix.
Pour batter into greased muffin tins or silicone liners.
Bake for 15-18 minutes, until a wooden toothpick comes out clean.
Remove from oven and let the muffins cool on wire rack.