you can also achieve it with two Xbowmen units on (manual) skirmish against a heavy cav (works best the heavier it is...)

But you'll have to micromanage those units...

First, try to determine which unit of Xbow the cav will charge then skirmish that unit away manually...

Try to remain at all times in the max range of your Xbow as it is longer than the charge distance of most heavy cav...

If they continue to advance on that unit, they will soon show their unprotected back to the second unit of Xbow...

Should they change and try to engage the second unit they will then turn their back on the first unit and bolts will rain down their back...

Repeat as much as necessary... and before long the cav (with quite a few casualties) will run away to get another target (if not rout...)

You might call this one a crossfire...