Toast Pecans: In a medium skillet over medium heat, melt 1 tablespoon butter. Add chopped pecans and 1/4 teaspoon salt. Sauté for 4 to 5 minutes until deeply fragrant and lightly toasted. Transfer to a bowl to cool completely.

Brown the Butter: In a light-colored saucepan, melt 1 cup unsalted butter over medium heat. Swirl occasionally as it foams and sizzles. After 5 to 7 minutes, amber-golden flecks will settle on the bottom and release a rich hazelnut aroma. Immediately pour browned butter (including all brown specks) into a heat-safe bowl and let cool for 20 minutes.

Whisk Wet Ingredients: In a large bowl, whisk cooled brown butter, dark brown sugar, and granulated sugar vigorously for 2 minutes until glossy and smooth. Whisk in eggs and vanilla extract until thick and pale ribbon forms.

Combine Dough: Fold in flour, baking soda, and fine sea salt with a rubber spatula just until no dry pockets remain. Gently fold in the toasted butter pecans.

Chill: Cover bowl with plastic wrap and chill dough in the refrigerator for at least 45 minutes to solidify fats and concentrate rich toffee flavors.

Bake: Preheat oven to 350°F (175°C). Line two baking sheets with parchment paper. Scoop 3-tablespoon mounds (about 55g each) spaced 2 inches apart. Bake for 10 to 12 minutes until edges are golden and set, but the center is still soft and puffy.

Finish: Remove from oven and immediately tap the baking sheet firmly on the counter to create ripple wrinkles. Sprinkle warm cookies with flaky Maldon sea salt and let rest on the sheet for 10 minutes before transferring to a wire rack.