Place a few wooden skewers in a bowl of water to soak for 30 minutes (or leave overnight the day before making the suya skewers).
Place a pan over medium-high heat. Pour in the peanuts, then toss and char until it's brown and toasted.
Pour the charred peanuts into a mortar and grind with a pestle into gritty bits. Add the ginger, garlic, chilli powder, nutmeg and salt, then grind until it's all combined. (The spice mix can be gritty or smooth as you prefer. You can also blitz in a blender or food processor).
Place the beef in a dish and season with a tablespoon of the suya spice mix and the sunflower oil. Rub the spices and oil into the beef slices, then wrap the dish in plastic wrap and leave in a refrigerator for 30 minutes to marinade.
Place the remaining spice mix in a jar to use later. Preheat oven to 200 degrees celsius.
After 30 minutes of marinating, pass each slice of beef through a skewer. leaving a 1/3 of the skewer empty to hold. Repeat with all the beef until they are all on a skewer.
Place the beef skewers on an oven rack and place them in a preheated oven. Also, place an oven tray with baking paper to catch the dripping juices from the meat. Grill in the oven for 30-40 minutes.
Once cooked remove the beef skewers from the oven. Scoop some of the leftover suya spice mix unto a flat dish and rub the beef skewers into the spice mix and serve.