1) Preheat oven to 375 degrees F. In a large bowl whisk together all-purpose flour, baking powder, salt, and cinnamon.
2) In a medium bowl, mash bananas well until they are almost no lumps. Add in sugar and continue to mash until well combined. Then stir in eggs, milk, and melted butter.
3) Stir wet ingredients into the dry ingredients. Add poppy seeds and stir until combined. If batter is very thick and not pourable, add more milk by the tablespoon to loosen it.
4) Divide batter into 12 muffin tins (greased with butter). Fill muffin tins almost to the top.
5) Bake muffins at 375 degrees F. for 20 minutes.
6) Finished muffins should be browned on the edges and puffed in the center. Feel free to test one with a tester. The center should be completely set in each muffin.
7) Let muffins cool for a few minutes, then remove and serve warm. Store extra muffins in an air-tight container in the fridge for 4-5 days.