In a mixing bowl, cream together butter butter, oil and sugar. Then add in the eggs and vanilla.
In a separate bowl, mix together the flour, salt and baking soda.
Add the bowl of dry ingredients to the mixing bowl of 'wet' ingredients. Stir together until mixed well. Add the chocolate chips.
Spread cookie batter in the greased pan. Put in oven, set timer for 5 minutes.
Once the 5 minutes is complete, take pan out and swirl the cookie batter with table knife, especially the edges of the pan. Swirl well so melted chocolate chips are mixed well.
Put pan back in oven for 10-12 minutes until done. They will be medium brown & raised in center when done. Enjoy!