Preheat your oven to 350°F (175°C). Line two large baking sheets with parchment paper. If your pecans are not pre-toasted, spread them on a baking sheet and toast in the preheated oven for 5-7 minutes, until fragrant. Let them cool completely, then chop them if not already chopped.

In a large mixing bowl, using an electric mixer, cream together the softened unsalted butter, granulated sugar, and light brown sugar on medium-high speed until light, fluffy, and pale in color, about 2-3 minutes. Scrape down the sides of the bowl as needed.

Beat in the eggs one at a time, mixing well after each addition. Stir in the vanilla extract until just combined.

In a separate medium bowl, whisk together the all-purpose flour, baking soda, and salt. Make sure there are no lumps.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined and no streaks of flour remain. Be careful not to overmix.

Fold in the cooled, chopped toasted pecans using a rubber spatula until evenly distributed throughout the dough.

Cover the bowl with plastic wrap and refrigerate the cookie dough for at least 30 minutes. Chilling helps prevent the cookies from spreading too much and ensures a chewier texture.

Once chilled, drop rounded tablespoons (or use a 1.5-inch cookie scoop) of dough onto the prepared baking sheets, leaving about 2 inches between each cookie. Do not flatten the dough balls.

Bake for 10-12 minutes, or until the edges are lightly golden brown and the centers are still soft and slightly underbaked. The cookies will continue to set as they cool.

Remove the baking sheets from the oven and let the cookies cool on the sheets for 5 minutes before transferring them to a wire rack to cool completely. This step is crucial for the cookies to firm up without breaking.

Serve warm or at room temperature and enjoy your soft and chewy butter pecan cookies!