In a pestle and mortar grind the cloves and cardamon pod seeds, then finely slice the onions. Place a large sauce pan on a medium heat and add the oil and butter. When the butter begins to foam and all the ground spices including the clove and cardamon mix. When the aroma of the spices start to release add the onions and gently fry until soft and brown, this may take 20 - 30 mins so be patient and don't let them stick. If the mix starts to look a little dry add a little water.