Add the butter, brown sugar, and granulated sugar to a bowl and mix until creamy. Add the egg and vanilla extract and mix until smooth.
Add the flour, salt, and baking soda. Mix just until combined, then fold in the chocolate chips.
Chill the dough for at least 2-3 hours (preferably overnight). Divide into 12 equal portions.
Roll into balls and place them on a baking sheet with enough space between them. You’ll likely need two baking sheets. Press a few extra chocolate chips into the tops (see tips for two methods).
Bake in a preheated oven at 340°F/170°C (conventional oven) for about 14 minutes, until golden brown. The cookies will still be slightly soft. Let them cool on the baking sheet for a few minutes, then transfer to a wire rack to cool completely.
Tips
You can press extra chocolate chips into the dough balls before baking, or add them right after baking while the cookies are still soft.
How to store
Store in an airtight container at room temperature for 1-2 weeks.