Bring a large saucepan of salted water to the boil, add linguine and cook 12 to 13 minutes, or as instructed on the package until al dente. Drain.
Meanwhile heat olive oil in a large frying pan over medium heat and cook and stir the onion until soft. Add garlic and prawns and fry, stirring constantly. When the prawns are turning pink, sprinkle with cayenne and oregano and fry for another minute.
Wash spinach and keep a little wet. Add in batches to the frying pan and and cook until wilted. Add cream, heat through then add salt and pepper to taste.
If you want a thicker sauce, pour some of the cream into a small saucepan. Heat up and stir in cornflour. Boil until thick and smooth stirring constantly. Pour the thickened sauce back into the pan with the prawns, add pasta and toss. Serve immediately.