For this, I use Shan's Karachi beef Biryani mix (can be bought from any Indian/Pakistani convenience store). I use chicken however- a whole chicken cut up into Biryani pieces. The difference is, it does not call for tomatoes but I add in 1 to 2 chopped tomatoes once the onions start browning. Make sure to NOT use the amount of oil they mention on the box- use half! So brown the onions and then add the tomatoes along with the spice mix, chicken and everything else as per the instructions. The important thing is if you're adding tomatoes, only add 1/2 to 1 cup water in. It is important to cook the chicken on high at first and then super low for a long time while covered. The flavours really seep in! The other thing is, when I boil the rice (and using perfect, aged, basmati rice is of course key duh), I add in 2 bay leaves, some, cloves, some black peppercorns, 2 or 3 cardamoms, 2 cinnamon sticks along with the salt when boiling. I can't tell you what a difference this makes in the flavour of the biryani is a whole. Once you follow the rest of the steps (3/4 cooked rice and all that jazz), layer the masala (gravy) and the biryani in a casserole dish and add sliced tomatoes, coriander, and green chilies and cover with foil or a tight lid and place in a preheated oven at 350 to 375 for about 25 minutes. Take out and mix before serving. SO GOOD! Slurp!