Tip the soup mixture into a food processor or blender (or use a hand blender) along with the remaining spinach, and blitz until smooth. Season to taste with salt, pepper and the lemon juice. Will keep chilled for three days. When ready to serve, reheat on the hob until piping hot. Drizzle over a little cream in a spiral, then drag a skewer through the cream to create a spiderweb effect. Scatter over the croutons to serve.
