Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper or silicone baking mats.
In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
1 cup unsalted butter, 1 cup granulated sugar, 1 cup brown sugar
Beat in the eggs one at a time, then stir in the vanilla extract.
2 eggs, 2 teaspoons pure vanilla extract
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt until well combined.
2 cups all-purpose flour, 3/4 cup unsweetened cocoa powder, 1 teaspoon baking soda, 1/2 teaspoon salt
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the chocolate chips and chopped pecans until evenly distributed throughout the cookie dough.
1 cup semi-sweet chocolate chips, 1 cup pecans
Chill the dough in the refrigerator - covered - for an hour minimum.
Using a cookie scoop or spoon, drop rounded tablespoons of dough onto the prepared baking sheets, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes, or until the edges are set and the centers are still slightly soft.
Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to wire racks to cool completely.