In a stand mixer or large bowl mix butter, brown sugar and egg thoroughly. Stir in flour and baking soda (the dough will be stiff). Stir in chocolate chips just until incorporated. Drop dough by rounded tablespoonfuls about 2 inches apart onto a cookie sheet. Bake for 8-10 minutes, or until lightly golden brown. The centers will be soft.
Remove from oven and let cool for 5 minutes before serving.