Everyone has their own opinion on whether a chocolate chip cookie should be crunchy or chewy. There is of course no right answer and is purely a matter of choice. How your cookies turn out, if you bake them yourselves, is largely down to what goes into them and how long you bake them. Below is what I've found out through others posts and by experimentation.
Cookies made with butter will spread out more because butter has a lower melting point. As they will be thinner they will cook quicker and be of a uniform texture most probably on the crispy side.
Cookies made with margarine, shortening or even oil will hold their shape better so will be thicker. If these are slightly undercooked and left on the baking sheet for a short while once removed from the oven, you should get that characteristic crunchy edge and chewy centre.
So the fatter the cookie the chewier it will be - not rocket science really!
Different sugars also give differing results. For example, all white sugar gives a crispier texture than if light or dark sugars are used. Many recipes combine the two for flavour and texture.
The type of chocolate used e.g milk, dark or white doesn't really affect the texture but the size of chunks should reflect the size of the cookie.
Cooking temperature is around 180 degrees C 350 degrees F. The temperature of the dough when it goes in the oven does affect the amount a cookie spreads. Warm dough obviously spreads more and chilled less. I sometimes but the prepared cookies on the sheets into the freezer for a few minutes and this tends to slow the spread giving nice chunky chewy cookies.
The Martha Stewart Double Chocolate Chunk cookie recipe is very good but you'll have to convert to UK measures.