Bring 1 1/2 cups/375 ml water to a boil in a saucepan with a pinch of salt. Add the peas, bring back to a boil, cover and cook until soft, about 10 minutes. Blend to a puree with an immersion blender. Strain into a clean saucepan. Stir in the cream, reheat and season with salt and pepper. Sprinkle with mint and Parmesan if using.