Measure out the spices and place them right next to the stove in separate piles. Heat the oil in a large skillet over medium-high heat until very hot. Add the fenugreek seeds and fry until they turn dark brown (about 10 seconds) add the asafetida, coriander, and pepper. Stir once and immediately add the squash. Stir rapidly to distribute the spices (about 3 to 4 minutes). Sprinkle on salt to taste; stir. Lower the heat and cook, covered, until the squash is cooked but still holding its shape (about 15 minutes). Uncover and sprinkle on the mango powder. Reduce the heat to medium and turn-fry for 2 minutes. Add the jaggery and cook until it melts and coats the vegetables (3-4 minutes). Serve warm, at room temperature, or cold. Classic Indian Vegetarian and Grain Cooking, Julie Sahni per Mimi Taylor.