In a large mixing bowl, beat together the melted, cooled butter with both the granulated and brown sugar. Mix on medium speed until the mixture is creamy, smooth, and noticeably lighter in color.

Crack in the eggs and pour in the vanilla extract. Continue mixing until everything is fully incorporated and the dough is silky and uniform.

Add the all-purpose flour, cinnamon powder, cornstarch, baking soda, and baking powder to the wet ingredients. Stir gently, just until no streaks of flour remain—avoid overmixing.

Gently fold in the chopped pecans and, if using, toffee bits. Stir until the mix-ins are evenly spread throughout the dough.

Cover the bowl and refrigerate the cookie dough for 30 to 45 minutes.

Scoop out portions of chilled dough (about 1.5 tablespoons each) and gently roll into balls.

If you enjoy an extra-sparkly exterior, roll each dough ball in a small bowl of granulated sugar before baking. Totally optional!

Arrange dough balls on a parchment-lined cookie sheet, leaving a couple of inches between each for spreading.

Bake at 350°F (175°C) for 11 to 14 minutes. Let cool, then enjoy warm or at room temperature!