Bolas de Banana Verde ao Masala

4 green bananas 250g potatoes 3cm grated or finely chopped fresh ginger 1 teaspoon nigella oil 1/2 teaspoon toasted and freshly ground black pepper 1 tablespoon all-purpose flour Salt to taste Ghee for dipping Sauce: Ghee to taste 1 tablespoon yogurt 1 pinch asafoetida 1 dried red chili flakes 2 green cardamom pods (seeds only) 1 crushed clove 1 cinnamon stick Salt and sugar to taste