Step 1: In a large mixing bowl, cream together the softened unsalted butter, granulated sugar, light brown sugar, and dark brown sugar on medium speed until light and fluffy, about 2-3 minutes.
Step 2: Beat in the eggs one at a time, mixing well after each addition. Stir in the vanilla extract, scraping down the sides of the bowl as needed.
Step 3: In a separate medium bowl, whisk together the all-purpose flour, baking soda, ground cinnamon, and salt.
Step 4: Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Do not overmix.
Step 5: Gently fold in the toasted chopped pecans until evenly distributed.
Step 6: Cover the bowl with plastic wrap and refrigerate the cookie dough for at least 30 minutes, or up to 2 hours, for best results.
Step 7: Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.
Step 8: Scoop rounded tablespoons of dough onto the prepared baking sheets, leaving about 2 inches between each cookie.
Step 9: Bake for 10-12 minutes, or until the edges are golden brown and the centers are still slightly soft. They will continue to set as they cool.
Step 10: Let the Pecan Pie Oatmeal Cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely. Store in an airtight container at room temperature for up to 5 days.