Begin by peeling and chopping the sweet potatoes into small cubes. Add them to a steamer and steam until soft which should take about 10-15mins.
While the sweet potatoes are steaming, add the cashews to a bowl and cover with just boiled water.
You can also cook the pasta as per packet instructions while you are waiting for the sweet potatoes to steam.
Once the sweet potatoes have become soft and the cashews have been soaking for at least 15 mins in the boiling water, add them to a food processor, together with all the remaining ingredients (exluding the pasta!) and blitz until smooth.
Drain the pasta and pour the blended sauce mix into the pasta. Add a sprinkling of black sesame seeds and season to taste.