I use this recipe frequently and it is fantastic. The spice proportions are great although I do add a small pinch of ground cloves. And as a suggestion, if you are grinding your own lamb, and I suggest you shouldn't make Kibbee Nyi if you're not, put the lamb cubes in the freezer for 10-15 minutes first and it will grind so much better.
This is very good approximation of raw kibbee and I agree with the poster that you must use the very leanest and best quality meat. I use either cubed lamb stew meat or boneless leg of lamb, cut into chunks and then run though fine disk of grinder. I use 1 teaspoon of coarsely ground white pepper, 1/2 teaspoon of allspice and 1/4 teaspoon of the cinnamom for the perfect seasoning balance along with the mint leaves specified, although it is still good without the mint.