If you don't have or can't get fresh chillies, I have used the 'lazy chillies' and it is still very nice.
You can 'brown' off the chicken before you put into the slow cooker if you want to. I feel that putting everything in at the same time gives almost a marinating time.
I found this recipe to be very tasty and would suggest to kathjdyer who though it was 'blah' that it was the preparation rather than the ingredients that caused it to be bland. You can't just put everything in a slow cooker and expect good results. The way I cooked this recipe involved a number of stages of pre-cooking. I coated the chicken with plain flour and browned it in a large frying pan using ghee. The flour helps to brown the chicken and adds some thickening to the sauce. I added the chicken together with the pan's contents, juices, ghee and flour into the cooker. I stir fried the onions, garlic, peppers and chilli in ghee for about five minutes until just beginning to soften and then added all the spices and curry powder(I used Co-op's own brand medium), and continued to stir fry to release all of the spices' flavours. To place spices directly into water simply drowns their flavours. I added this to the cooker and swilled the pan out with the 300ml of water boiled adding it to the cooker so that nothing was left behind. I added the tin of tomatoes. There is no salt in the ingredients and nothing makes a curry so bland as the lack of salt. I added one teaspoon of salt but it possibly needed one and half, maybe two. People that are used to jar or take away curries may find this to be on the watery side. My wife, who is of Indian parents, cooks traditional curries and they are all of this consistency. Evidently the 'gravy' is soaked up with roti(chapati). - 05 Jul 2010
I made a big old pot of this by doubling all the listed ingredients except the water, sticking to 300ml (so in effect half). I also added in a few carrots, some cauli and baby corn to boost the veg content. We ate it with chipatis and rice and it was delicious (AntJin is right, this is how exactly how it comes in India and the consistency was perfect, although some may think it watery). This made plenty for 4 people and some for the freezer for a lazy day. I will definitely make this again, the best curry I've had since I was in India! Note - I did fry up the onions, garlic, peppers and chilli with the spices before adding to the slow cooker. I didn't brown the chicken though. - 19 Nov 2010