Preheat oven to 350F. Line 1 small baking sheet and 2 large baking sheets with parchment paper.
Spread the pecans out over the small baking sheet and bake for 8 to 10 minutes or until wafting a rich toasted scent. Let cool slightly. Then, add 3/4 cup of the toasted pecans to a food processor. Process for 4 to 5 minutes or until smooth and glossy, stopping to scrape down sides as needed. Meanwhile, chop the remaining 1/2 cup pecans and reserve.
In a medium mixing bowl, beat together the pecan butter, coconut sugar, brown rice syrup, and vanilla extract for 1 minute using a hand or stand mixer.
In a small mixing bowl, whisk together the oat flour, baking soda, baking powder, and sea salt. With the mixer off, add the dry ingredients to the creamed pecan butter mixture. Then pour the almond milk over the flour mixture and turn the mixer on low. Increase speed to medium-low and beat for 30 seconds or until just incorporated. Stir in the chopped pecans. Place the entire mixing bowl in the freezer and chill the dough for 30 minutes or until it reaches a scoopable consistency.
Use a cookie scoop or two tablespoons to scoop out approximately 2 tablespoons of dough. Drop on baking sheets, leaving at least 2 inches in between each mound of dough. You should have about 15 cookies, and no more than 8 cookies per baking sheet. It's okay if the dough starts to spread out before baking. Bake for 10 to 14 minutes or until just turning golden-brown, rotating pans at the 5-minute mark. They will spread out thin, and this is what you want.
Cool completely on the pan before moving or enjoying.
To store: place single layers of cookies between sheets of parchment paper.