Preheat the oven to 375°F and line a 12-cup muffin tin with paper liners.
Place the thawed spinach in a clean kitchen towel and squeeze until very dry. You should have about 1 cup packed spinach, and removing the water is the key to light, fluffy muffins.
In a large bowl, whisk together the flour, baking powder, baking soda, salt, oregano and pepper.
In a separate bowl, whisk the cottage cheese, eggs, milk, olive oil, garlic and lemon zest.
Stir the wet mixture into the dry ingredients until mostly combined. Add the spinach, pulling it apart to break up clumps, then fold in 3/4 cup feta, the green onions and dill just until no flour remains.
Divide the batter among the cups and top with the remaining feta and sesame seeds.
Bake for 22-25 minutes, until golden and a toothpick inserted in the center comes out clean.
Cool in the pan for 5 minutes, then serve warm. They are great on their own or with a spoonful of tzatziki.