Preheat the oven to 375°F with two racks close to the center.
In a large bowl, beat together the butter and both types of sugar with an electric mixer until lightened in color and texture, about 3 minutes.
Add eggs and vanilla and beat until combined.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
Add the dry ingredients to the wet ingredients and stir together with a wooden spoon or silicone spatula.
Add the oats and stir to combine. Dough will be very thick.
Stir in the chocolate chips, Hershey's bars, and nuts.
Using your hands or a couple of spoons, form the batter into loose, golf-ball-sized mounds. Place two inches apart on ungreased cookie sheets.
Bake for eight to nine minutes, until tops are just golden and cookies are still soft.
Transfer to a wire rack to cool at least slightly before serving.
