Heat the oil and butter in a large pan over a medium high flame. When hot add the fennel seeds and cardamon pods. Stir once, then add the onions and ginger.
Stir and fry until the onions turn a rich brown colour then add the spinach. Cover and allow to wilt completely. Stir every now and then.
When wilted, turn the heat to medium and add the salt and chilli powder. Cover and cook for 25 minutes.
Remove the lid and add the garam masala. Cook and stir, uncovered, for about 5 minutes or until most of the liquid has evaporated.