Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a large bowl, whisk together the melted butter, granulated sugar, and light brown sugar until smooth and combined.
Add the egg and vanilla extract to the butter and sugar mixture. Whisk until fully incorporated.
In a separate medium bowl, sift together the all-purpose flour, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined. Do not overmix.
Fold in the semi-sweet chocolate chips evenly throughout the dough.
Using a tablespoon or small cookie scoop, drop rounded spoonfuls of dough onto the prepared baking sheets, spacing them about 2 inches apart. Flatten each dough ball slightly with the back of a spoon or your fingers to encourage a thin, crispy texture.
Bake in the preheated oven for 10 to 12 minutes, or until the edges are golden brown and the centers look set but still slightly soft.
Remove the cookies from the oven and allow them to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.
Store the cooled cookies in an airtight container at room temperature for up to 5 days.