Beat together butter, sugar, salt, and baking soda in a large bowl with an electric mixer until fluffy, then beat in egg and vanilla.
Add flour and mix at low speed until just combined. Fold in chocolate chips.
Drop barely rounded 1/2 teaspoons of dough about 1 1/2 inches apart onto ungreased baking sheets and bake in batches in middle of oven until golden brown, 6 to 7 minutes.
