Chop off its head! Grab a few stems and snip off the top sections.

The reason some suggest cutting the outer stems down as you describe, is that you're using up the older growth first, allowing the plant to produce more young growth. It doesn't really matter which method you choose. Harvesting parsley isn't rocket science!

With curly parsley, I always recommend taking the outer leaves first. Its growth pattern is somewhat like a volcano - new growth bursting up through the middle, and older growth flowing down the sides. Makes sense to take those flowing down the sides, doesn't it? To make room for the newer growth to follow suit.

Parsley grows from the ground. It does not have branches with nodes where new buds form unlike many plants, eg thyme or sage. Therefore cutting off some of the leaves and leaving a few will not promote bushier growth on a particular stem because there are no buds-in-waiting to grow. Just cut or pull the stems low down and new ones will come up out of the ground.

To add to what has already been said, the general rule of thumb is not to harvest more than 1/3 of the living plant material at any one time on plants that you want to keep growing. More than 1/3 and the plant may not bounce back at all or at least not very well.

FataMorgana