Place the butter in a medium saucepan. Cook over medium heat, stirring often, until brown specks form on the bottom and it smells nutty. Remove from the heat and transfer to a large mixing bowl. Cool to room temperature (about 15 minutes).

Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper or silicone liners.

In a medium bowl, whisk together both flours, baking soda, and salt. Stir in the oats. Set aside.

Using an electric mixer on medium speed, add the brown sugar to the cooled butter and mix until combined. Add the egg and the yolk, one at a time, mixing well after each. Beat in the maple syrup, vanilla, and maple extract (if using).

Reduce mixer speed to low and gradually add the flour-oat mixture just until combined. Stir in the pecans.

Scoop the dough into 3-tablespoon portions and place on the prepared pans, spacing about 2 inches apart. Flatten each slightly with your hand or the bottom of a glass.

Bake one pan at a time for 12–14 minutes, or until the edges are lightly browned and the centers look just set. For chewier cookies, err on the shorter side.

Let the cookies cool on the pan for 5 minutes, then transfer to a wire rack to cool completely.