Place the cooking pot back on medium heat and add oil. Let warm up. If you are using mustard oil, warm up for a little longer so that the raw smell of oil goes away.
Temper the warm oil with bay leaf, cinnamom stick, hing and black cardamon. Also add the ginger. Fry everything on low heat for 5-6 seconds taking care not to burn the spices.At this stage you can also add few slit green chilies (hot variety) for extra heat. Add the sliced onions next. On medium flame,fry the onions for about 8-10 minutes or until they are golden brown. Don't rush the onions, the right amount of browning contributes to the color and taste of curry.
Reduce the heat to low, and sprinkle 1.5 teaspoon kashmiri red chili powder along with 1-2 tablespoon of water (to avoid the chili powder from burning). Stir and fry for a minute or so taking care not to burn the chili powder. If needed, take the cooking pot off the stove.
Next, add the par boiled potatoes and sprinkle salt on them. Toss around and fry the potatoes with onions for about 3-4 minutes on low medium heat. In this way, introducing potatoes a bit early starts the flavor absoprtion rightaway.
Then, add the tomato puree & sugar. Continue to fry the potatoes with masala for 3-4 minutes.
Once you see that the moisture of tomatoes has evaporated a little bit, reduce the heat and add the beaten yogurt. As soon as you add the yogurt, start stirring and continoue for at least 2 minutes or until the yogurt has warmed through. This prevents the yogurt from curdling.
Once yogurt is part of the masala, add the spice mix that we made earlier. Mix everything and fry for another 1-2 minutes.
When you see oil starting to seperate, add about ¾ cup water (warm water). Don't add too much water since aloo dum has a thickish gravy.
Mix and then cover the cooking pot and let dum cook (slow cook) on low flame for about 12-14 minutes or until the potatoes are cooked through. Check 2-3 times while slowcooking and make sure that the masala is not getting too dry. Add water as needed. Make sure that the potatoes dont over cook, please adjust slow cooking time accordingly.
Once the potatoes are fully cooked, open the lid.You will see a thin layer of oil on the sides of pot and the potatoes will have a beautiful color.
Finish aloo dum with crushed kasuri methi. Let rest for 10-15 minutes if possible.