There's been some talk on donrockwell.com about this Persian place in Mclean which used to have the same menu as Shamshiry, a sister restaurant. It is now owned by the family that ran (but has sold) Rose Kabob in Vienna.
Rose Kabob was maybe the best Persian restaurant in the DC area, and now that is probably true of Amoo's. It is stellar.
For only $10, the tadig topped with your choice of stew (get the geymeh) is a Top 5 all-DC bargain. The mast-o-mousir yogurt is exceptional, so don't forget about that.
Finally, Mclean has a terrific restaurant.