To cut the escalopes: with a long sharp knife, cut the salmon fillet in to the largest possible diagonal slices, about 1/4 inch thick, working towards the tail and discarding skin.

To cook the julienne: bring a pan of salted water to the boil, add the carrot and leek juliennes and boil until tender but still firm - 3-5 minutes. Drain, rinse with cold water and drain again thoroughly. The salmon and vegetables can be refrigerated for up to 4 hours.

Sprinkle the escalopes with salt and pepper. Heat a large non-stick frying pan until hot, then brush it with butter. Add as many escalopes as will fit in a single layer and cook until lightly browned - about 1 minute. Turn them and brown the other side. Remove from the pan and keep them hot while cooking the remaining escalopes in the same way.

Add the cream to the pan and bring it to the boil. Whisk in the mustard, salt and pepper. Add the julienned vegetables and heat gently for 2 minutes. Stir in the tarragon and taste the sauce for seasoning.

Arrange the scalopes on individual plates, allowing 2-3 per person. Spoon over enough sauce to cover the salmon partly and decorate with tarragon sprigs.