Preheat oven to 350°. Butter 12 muffin cups (1/3-cup size) and set aside. Put sesame and poppy seeds in a pie pan and sunflower and pumpkin seeds in another. Bake seeds, stirring once, until golden, 6 to 8 minutes. Combine seeds in 1 pan and set aside.
Whirl dates with 1/2 cup water in a blender or food processor until very smooth. Scrape into a medium bowl and add bananas, yogurt, oil, vanilla, egg yolk, and 3/4 cup sugar. Whisk to blend, then set aside.
Stir flours in a large bowl with flaxseed meal, baking powder and soda, salt, and all but 2 tbsp. of the seeds.
Beat egg whites with cream of tartar in a bowl with a mixer on high speed until foamy. Gradually add remaining 1/4 cup sugar, beating until soft peaks form. Fold whites into banana mixture. Fold into flour mixture just until blended. Spoon batter into prepared muffin cups (they'll be very full). Sprinkle with remaining 2 tbsp. seeds.
Bake muffins until just firm to touch and edges are golden, 22 to 25 minutes. Loosen from pans with a small metal spatula. Serve warm or cool.
These were a bit of work with the pureeing of the dates with water and then the mixing of egg yolks and cream of tartar, but I decided that the first time I made them (yes, I WILL make these again they were soooo yummy), I'd more or less follow directions. I did not have sesame or poppy seeds and they were just fine without them. I maybe didn't bake them long enough because they not as firm as muffins should turn out. I just didn't want to run the risk of over baking them and drying them out, though. Still, they were so darn tasty that I ate 3 in a row!
Very tasty. A little sweet for my taste. I'd cut the sugar by 1/4 to start, if I made again. Definitely takes some time and the whipping of egg whites is rather finicky. A good Sunday morning recipe. Wish the nutrition info listed fiber.