Preheat oven to 350°F (175°C). Butter two 6- or 8-ounce ramekins* (or coat with a cooking spray).
Whisk together the flour, baking soda, and salt. Set aside.
Stir together the cooled butter, brown sugar, vanilla, and egg until thoroughly combined.
Add the flour mixture, and mix just until combined or a few streaks of flour remain.
Stir in the chocolate chips.
Divide the batter between the ramekins, spreading evenly. Bake 20 to 25 minutes, or until the edges are browned and the center appears set.
Serve warm with your favorite toppings.
Notes
*The cookies pictured here were made in 6-ounce ramekins, which is a bit of a tight fit. If you're worried about them baking over the top, use 8-ounce ramekins. You can also easily make these as 4 servings with four 4-ounce ramekins.
Store in an airtight container at room temperature up to 2 days.