Bring a pan of well-salted water to the boil and add the potatoes, thyme and garlic. Boil steadily until cooked through, about 12-15 minutes, and test with a knife. Drain the potatoes and peel while warm. Place in a bowl, cover and chill.
In a small bowl, whisk the white wine vinegar, olive oil and a couple of pinches of salt together to make a vinaigrette. Cut the cold potatoes into thick slices, add to the dressing and toss gently to coat. Leave to marinate in the fridge for at least 30 minutes, up to an hour.
For the horseradish cream, lightly whip the cream in a small bowl until thick then fold in the horseradish sauce. (If you have bought extra-thick double cream, just stir in the sauce). Cover and chill.
Check the smoked trout for small bones, removing them with tweezers, then use two forks to break into bite-sized pieces.
Halve the avocado, remove the stone and peel off the skin. Cut the flesh crossways into slices, season with salt to taste and drizzle with the lime juice.
To serve, layer the potatoes, avocado and trout in neat piles around the serving plates. Top with radish slices, dill leaves and thyme sprigs, and pea shoots or baby salad leaves. Drizzle with olive oil and serve with a dollop of horseradish cream, sprinkled with a little black pepper.
Jason Atherton, Michelin-starred chef, brings inexpensive, accessible gourmet food into the home kitchen. His creative style and mastery of unique flavours makes his cooking exciting, delicious and highly original. Click here to purchase his latest book Gourmet Food for a Fiver.
See more Starter recipes