Wash, dry, and peel the sweet potatoes. Grate the sweet potatoes, place in a bowl and set aside.
Using a food processor or dry spice grinder, grind the walnuts until they are coarsely ground. Be careful to not over-process; you don’t want them to blend to a nut butter consistency. You may also coarsley chop them.
Melt the ghee in a large frying pan over medium-high heat. Add the cumin seeds and let them temper in the hot oil for 15-30 seconds. Add the chili peppers and fry for 15 seconds, until slightly browned.
Add the grated sweet potatoes to the pan and sauté for 5 minutes, until softened. Season with the salt and mix until well combined.
Reduce the heat to medium-low, cover, and cook for 5 minutes, until almost cooked through.
Uncover, raise the heat to medium-high, and stir in the walnuts and lemon juice. Using a spatula, press down on the mixture, flattening it against the bottom of the pan. Continue to cook for 3 to 5 minutes, until a slight crust forms. Remove from the heat.
Garnish with the cilantro and serve immediately.