... says Nigella Lawson, is the amount of chocolate chips you add to your batter. She admits to using two packs of morsels/chocolate chips when she bakes her chocolate cookies and defends the indulgence by saying that "she doesn't put a price on alleviating human suffering".
I'm sure nobody will contest that!
But if you're not really willing to spend so much on chocolate chips/morsels/drops... my sister-in-law swears that it's the cocoa you use for the batter that really spells the difference. You can use any morsel brand you want, or even replace them with sprinkles, nuts or fruit, but if the cocoa you used isn't a trusted brand, the cookies will fall short.
We mostly use Hershey's cocoa for our baking requirements.