Preheat oven to 370 degrees and line a baking sheet with parchment.
In a mixing bowl whisk together the oat flour, oats, baking soda, and sea salt, if using.
In a small bowl combine the tahini, coconut sugar, milk, maple syrup, vanilla, and most of the rosemary (reserve just a pinch of rosemary to press into the tops of the cookies). Add tahini mixture to the dry ingredients and stir until combined. Fold in chocolate chips, if using.
Use a small cookie scoop (I use this 1.5 Tbsp scoop) or a spoon to scoop up approx 1 ½ tablespoons of dough per cookie. Gently smooth the ball of dough in your palms and flatten slightly. Place on cookie sheet 2 ½ to 3 inches apart; they will spread during baking. Then, just to ensure the rosemary is visible, press the reserved pieces of chopped rosemary into the tops of the cookies wherever needed.
Bake 10 to 12 minutes or until golden. Cookies are very soft straight from the oven. Let stand 5 minutes, then transfer to a cooling rack.
Once cool, store cookies in an airtight container at room temperature for up to 3 days. They can also be kept in the refrigerator or frozen for up to 2 months.