Prepare the satay sauce by putting all the ingredients (except for the beef) in a food processor and pulse for a few seconds. Thread the beef cubes onto the wooden skewers and brush the meat all over with the satay sauce. Pour any remaining sauce over the top and leave to marinate in the fridge for an hour or so. Just before you want to cook the satay beef skewers, prepare the salad. In a pester and mortar, crush together the garlic, ginger, red chilli and brown sugar to a pulp. Put this paste into a large bowl, along with the lime juice, rice wine vinegar and the oil. Mix these ingredients together to create a dressing for the salad. Add in the salad leaves, basil leaves, walnuts and mango slices and mix well. All that is left to do is cook the beef satay skewers. Heat up a griddle pan with a little oil, and cook the beef skewers on all sides till cooked through. Only a few minutes of cooking time is enough as the beef fillet will cook very quickly. When the beef skewers are cooked, serve the Thai walnut and mango salad in 2 deep salad bowls, each with two satay beef skewers on top.