Heat the oil in a frying pan on medium high heat. Test the heat by adding one cumin seed to the oil; if it cracks right away oil is ready. Add cumin seeds as cumin seeds crack, add all the ingredients, potatoes, red pepper, green chilies, cilantro, and coriander powder, mix it well while stirring the mix keep pressing. Filling should be not very dry, this should take about 5 minutes. Stir in garam masala and amchur. Add more salt or amchur according to taste. Let the filling cool to room temperature, mix it well this should have texture of firm dough.