My method is to get a big mass of strong, tough infantry, and a bunch of archers. 20 each of Nord Huscarls and Nord Veteran Archers works fine.
On top of that, I take 10 swadian knights, and a few companions in plate armour with bows on horseback. My character's set up as a horse archer with a big sword as backup.
What I do is find a nice spot to have the infantry and archers stand together. Somewhere that slows the bastards down, but not so much they stand off and hurl arrows and javelins constantly. The top of a steep-ish hill, a valley, or a river work fine. Hold this position, stand closer.
Then I tell the cavalry to follow me, and charge off to loop to the right side and around the back of the khergits, bombarding them with arrows (aiming for high-tier troops and coursers) and leading the knights through the flanks. After I've circled right around, I've aggroed their force, so they follow me back towards my infantry. I then lead them into the force of infantry repeatedly, sweeping in to take out any enemy horses standing in my ranks with my sword. All the while shooting arrows at them.
This continues until I run out of arrows, when I either go for playing chicken with the sword out, or gallop back to the baggage to refill. Eventually, they run down to a handful of troops, so I just tell everyone to charge and get on with mopping up the last few dehorsed buggers and the last few cavalry.
This doesen't work so well when they're got rhodoks and swadians and vaegirs in their ranks.
However, the strategy works against ANY cavalry. Take on caravans, lead the guards into your troops, then have the mass of infantry charge theirs.