In a skillet over medium heat, melt 3 tablespoons of unsalted butter. Add 1 1/4 cups of finely chopped pecans, toasting them until fragrant and golden (about 3-4 minutes). Remove from heat and let cool. Brown 2 sticks of unsalted butter in a saucepan, watching closely to prevent burning, then set aside to cool slightly.

In a mixing bowl, whisk together 2 1/4 cups of all-purpose flour, 1 tablespoon of cornstarch, 1 teaspoon of salt, 1 teaspoon of ground cinnamon, and 1 teaspoon of baking soda. Set aside.

In a large mixing bowl, combine the cooled browned butter with 1 cup of dark brown sugar and 1/2 cup of granulated sugar. Mix until smooth, then stir in 1 tablespoon of vanilla extract and the eggs, blending until creamy.

Gradually mix the dry ingredients into the wet ingredients on low speed until just combined, avoiding overmixing.

Gently fold in the cooled, toasted pecans with a spatula until evenly distributed.

Cover the bowl with plastic wrap or a towel and refrigerate for at least 1-2 hours, or up to 24 hours.

Preheat oven to 375°F (190°C). Line baking sheets with parchment paper. Use a cookie scoop to drop dough balls (1.5-2 tablespoons) onto sheets, spaced at least 2 inches apart. Bake for 9-12 minutes, until edges are golden-brown and centers are soft.

Let cookies cool on baking sheets for 5 minutes before transferring to a wire rack. Optionally, place a pecan half on each warm cookie.