Neiman Marcus style Chocolate Chip Cookies

yummy treat! preheat your oven to 350°F 2 & 1/2 cups rolled oats 1 & 3/4 cups all purpose flour 3/4 teaspoon salt 1/2 teaspoon baking powder 1 teaspoon baking soda 1 cup unsalted butter - at room temperature 1 cup granulated white sugar 1 cup brown sugar 2 eggs 2 teaspoon vanilla extract 1 (4 oz) chocolate bar 12 ounce semi-sweet chocolate chips 1 & 1/2 cup chopped walnuts (optional)