Preheat oven to 375° and line 2 baking sheets with parchment paper
Whisk together oats, flour, baking soda, cinnamon, and salt
In a separate bowl, whisk together brown sugar, white sugar, butter, egg yolk, vanilla and 1/2 cup water
Add flour mixture and mix until combined
Spoon out the dough onto your baking pans and flatten them to about 1/2 inch thick and 2 inches in diameter. Space them about 2 inches apart
Bake for 9 - 12 minutes until the edges are golden brown
Let cool completely on a wire rack