First begin with removing the skin of the lauki and then remove the seeds from the inside. If the lauki is tender, you will notice that they will have less seeds and also the seeds are very soft.
Next, using a box grater, grate the lauki. Measure the grated lauki. This measurement is what we will use to determine the amount of sugar to be used in the halwa.
In a medium saute pan, add the crumbled khoa / khoya / milk solids and cook it on low heat. You will notice that the khoa would start to release fat and will start changing color. Roast it for 2 to 3 minutes until light golden brown and then remove it on a plate.
In the same pan, heat a little ghee and fry the chopped dry fruits. Remove them on a plate as well and keep it aside until we are finished cooking the dudhi halwa.
Heat a wide pan on medium heat and add ghee. Add the grated lauki to the pan and start sauteing the lauki until it dries up a bit and also softens. About 5 to 7 minutes. (step 1)
Now add the milk and let it cook covered until the bottle gourd cooks completely. Then remove the lid and continue cooking until all the liquid evaporates. (step 2)
Add the sugar and mix well. (step 3)
You will notice that the halwa becomes liquid after the sugar is added. (step 4)
Keep cooking and then add saffron threads (step 5) and cardamom powder (step 6).
Once the dudhi halwa becomes semi solid, add the prepared khoa and fried nuts and mix well. (step 7)
Add the remaining ghee and keep cooking the halwa until it becomes thicker and starts to leave the sides of the pan.
Serve warm or chilled.