I suggest using whole small new potatoes rather than cutting up larger ones. Even fingerlings are good. Seems to avoid the uncooked problem. Another tip, which is a bit time consuming, is to soak potatoes (peeled) over night. That way when you cook then they will absorb all the flavor that boiled or microwaved will not do so well.
I agree with Jenny, the potatoes should be cooked first before attempting this recipe. Just got the amchur powder from an online site, (ishopindian.com), and it is excellent for dishes like this one.
This is almost a very good recipe. My big problem was with the potatoes going into the pan raw. That seemed strange to me, and so I microwaved them for 4 minutes first. In fact, when I try this again - which I will - I will boil them until tender before putting them in the pan. I needed to add much, much more water than called for, and more oil too, and my potatoes still came out of the pan very firm. I really liked the flavours though; this is my first time using amchur powder and I think it's really nice. I was a bit generous with both the amchur powder and the garam masala. I wish I had been less generous with the chili; in future I will put in the red chili powder OR the fresh green chilies, but not both. >:o Overall, though, this was simple and nice. I think it would be a great thing to do with leftover cooked potatoes.