My wife and i have been going to Sahebi Kabob when we are at the Markham and Steeles area and they remain the best place for afghan fare. The place might not look ritzy, but the food has always been great.
The best items are:
-beef tikka kebob
-chicken kofta kebob
-the spicy red tomato sauce is standard for dipping your naan bread and is amazing
There has yet to be place that can compare to their quality and value. They use sargent farms meats for those inquiring about the source. The only issue is that at times they are understaffed as it is family run casual restaurant.