To make the marinade, bash the peppercorn or uda pods in a pestle and mortar. Remove and discard the seeds, then place the pods into a liquidiser with the peanuts and spices. Crumble in the stock cube, then blitz for 5 to 10 minutes to a rough dry powder, stopping and stirring the mixture from time to time. Transfer the ground spices to a large bowl. Peel and roughly chop the onion, garlic and ginger. Trim and deseed the chillies and pepper, then roughly chop. Trim and roughly chop the spring onion. Add it all to the liquidiser and blitz until smooth. Transfer the mixture to the ground spices and stir well. Turn the beef in the marinade until well coated, then thread 4 to 5 slices onto each soaked skewer. Place on a tray, cover and pop in the fridge to marinate for around 3 hours.