Preheat the oven to 350 F. Microwave the butter for about 40 seconds. Butter should be completely melted but shouldn't be hot. In a large bowl, mix butter with the sugars until well-combined. Stir in vanilla and egg until incorporated. Add the flour, baking soda, and salt. Please read the recipe note about properly measuring flour. Mix dough until just combined. Dough should be soft and a little sticky but not overly sticky. Stir in chocolate chips.
Scoop out 1.5 tablespoons of dough (medium cookie scoop) and place 2 inches apart on baking sheet. Bake for 7-10 minutes, or until cookies are set. They will be puffy and still look a little underbaked in the middle.