Pressure cooking dal - Since I prefer the dal to be mashed up, I cook it for 8-10 whistles on medium - high flame. Switch off the gas. Let the pressure drop naturally, around 10-15 mins.
Keep in mind that dal tends to thicken as it rests, so adjust the qty of water accordingly. While reheating, add more water and reheat.
Though I strongly recommend using ghee for this recipe, you can also use oil instead of ghee for tempering. If you are using oil add a tsp of ghee in the end.
Though amchur powder gives a nice tang to the dish, you can also make this without it.