Stir together 2 cups whole-wheat pastry flour, ¾ teaspoon baking soda and ¼ teaspoon salt. In a separate bowl, beat 2 eggs, then stir in 3 mashed bananas, ½ cup brown sugar, ⅓ cup tahini, ¼ cup melted butter and 1 teaspoon vanilla. Combine wet and dry ingredients, then fold in ⅓ cup dark chocolate chips. Divide batter among 12 muffin cups, sprinkle with sesame seeds and bake 20 minutes at 350 F, or until a toothpick inserted in the center comes out nearly clean.