Bombay Potatoes

Ingredients

• 3 tablespoons sunflower oil
• 1 teaspoon mustard seeds
• 1 pinch ground cumin
• 1 teaspoon turmeric
• 1 teaspoon ground coriander
• 1 teaspoon garam masala
• 1 teaspoon chili powder
• 1 1/2 tablespoons fresh ginger, peeled and grated
• 1/2 cup butter
• 6 potatoes, peeled, parboiled and cut into smallish cubes
• 4 tomatoes, cores removed and flesh diced
• fresh cilantro, roughly chopped