This recipe was in a recent issue of Cook's Illustrated. My husband and I both LOVED it.
A few notes as well as some changes I made:
They suggest using whole milk yogurt, I could only find lowfat and it still tasted fine. I did not have the serrano chile it calls for, but I did put in a bit extra cayenne and it was still delicious.
If you do not have the garam masala they suggest you substitute the following: 2 teaspoons ground coriander, 1/4 teaspoon ground cardamom, 1/4 teaspoon ground cinnamon, and 1/2 teaspoon ground black pepper. (I had the garam masala on hand so I'm not sure if the substitute is good or not.)