Preheat your oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper and grease it lightly.

Melt 1 stick of unsalted butter over medium heat in a medium saucepan. Stir continuously for about 5 minutes until golden brown and nutty.

In a large mixing bowl, whisk together the cooled browned butter and light brown sugar until smooth. Stir in bourbon and vanilla, then add egg and egg yolk, beating until creamy.

Gently fold in all-purpose flour, ground cinnamon (if using), and salt into the wet mixture. Mix until just combined.

Incorporate toasted pecans and semi-sweet chocolate chunks into the batter.

Scrape the batter into the prepared baking pan and bake for 24 minutes. The edges should be firm, and the center should have a slight wobble.

Allow the blondies to cool in the pan for at least 1 hour. Sprinkle with flaky sea salt before cutting into squares.