Melt 2/3 cup chocolate in the microwave and let cool a bit.
Cream the butter and sugar until creamy.
Add melted chocolate.
Add egg and vanilla and beat until smooth.
Add dry ingredients and mix just until combined.
Stir in rest of chocolate chips.
Drop by medium ice cream scooper onto parchment lined cookie sheets,
Bake at 325 for 12-14 minutes
Adapted from Elinor Klivans