01 - Preheat oven to 350°F. Line 2 baking sheets with parchment paper or silicone baking mats.
02 - In a medium bowl, whisk together the all-purpose flour and fine sea salt until well blended.
03 - In a large bowl, combine the melted butter and granulated sugar. Whisk vigorously until the mixture is smooth and glossy.
04 - Add the egg, whole milk, orange zest, and vanilla extract to the butter mixture. Whisk until fully incorporated and the batter appears uniform.
05 - Pour the dry ingredients into the wet mixture. Stir gently with a spatula or wooden spoon until just combined. The batter will be thin and slightly runny.
06 - Drop rounded teaspoons of batter onto the prepared baking sheets, leaving at least 3 inches between each portion. The cookies will spread extensively during baking.
07 - Bake for 7 to 9 minutes, or until the edges turn golden brown and develop a lacy, delicate appearance. Monitor closely during the final minutes to prevent over-browning.
08 - Let the cookies rest on the baking sheet for 2 minutes to firm up. Gently transfer to a wire rack to cool completely before handling.
09 - If desired, drizzle melted dark chocolate over the cooled cookies or dip the edges. Allow the chocolate to set at room temperature before serving.