Mix the red onion with the vinegar, sugar and 1/4 tsp salt and set aside to lightly pickle for 20 mins.

Bring a pan of salted water to the boil over a medium heat and carefully tip in the green beans. Cook for 3-4 mins until tender but not soft, then plunge into a bowl of ice-cold water and leave for 5 mins. Drain thoroughly and pat dry.

Halve the baguette and spread any remaining avocado sauce over the base. Layer up the beef and greens and top with the green beans and pink pickled onions. Sandwich together and enjoy. Will keep chilled for up to a day.