Mix the sherry, alternatively the vegetable stock, with the orange juice, vinegar and the pulp of the vanilla pod, bring everything to the boil, season with sugar, salt and pepper and allow to cool.
Peel the asparagus, cut into 2 mm thin, diagonal slices and leave to stand in the marinade for 3 - 4 hours. Clean and quarter the strawberries.
Put the rocket, washed and dried, in a flat bowl and top with asparagus and strawberries.
Beat the marinade with the oil and drizzle the dressing over the salad.