My cookies are turning out like cakes
The original author is in error adding baking soda (bicarbonate), and indicating it will help rise.  For leavening, you require acid for the sodium bicarbonate to react with.  The original base recipe has no significant acid ingredients; even the modified version you used has only a trivial amount of acid from the molasses in the brown sugar.  

Therefore, the only effect of the baking soda is to increase the pH of the dough, which will encourage browning.  However, as the cookies are full of sugar, encouraging browning is not generally a problem.



The creaming method creates bubbles in the solid phase butter, and encourages rising and a more cake-like result, especially when paired with an effective leavening agent.

Resting the dough also hydrates the flour, and allows the butter to re-solidify, both of which inhibit spread and contribute to a higher cookie.

For a chewier result, do not use the creaming method.  Melt the butter instead, and then combine your ingredients. 

You may also choose to reduce the baking soda to reduce the metallic taste it brings without anything to react with.  

If the cookies are now too dense, you might try adding (starting with smaller amounts) 1/2 tsp  to 1 tsp or so of baking powder which has its own acid to react with, to help leaven the cookies.

See also:


What is the purpose of baking soda in chocolate-chip cookies?
How can I get chewy chocolate chip cookies?
How do I get my chocolate chip cookies to turn out thick and soft?