Our butter measures differently here in the Philippines and it is very salty. So based on the comments, I have adjusted the amount of butter to be slightly less than 1 cup and to call for salted butter. If your first batch still comes out flat, I would suggest adding more flour (up to ½ cup). These are not meant to be flat!
:) I tried baking these on two different pans - one was a cheap aluminum baking sheet and one was actually Calphalon brownie pan (!), and both kept the cookies nice and thick. When you first take them out of the oven, they will look more pale than a normal golden-brown cookie but that's normal. They start to look more even as they cool. These cookies should stay really thick and chewy even a day or two later. I like them stored in the refrigerator so they are firm and cold, but still buttery and soft. It's important to consider your altitude, humidity, oven tendencies, etc. when baking these. Here's a link
with some helpful tips for making adjustments at the bottom of the page.