Poached Trout, Creamy Mash and Watercress Sauce
By M&S Food
Published on 01 September 2025
Elliot Grover has created a light, flavour-packed plate with gently poached Loch Trout, served with a herby mash, grilled asparagus and a sharp gribiche and a silky watercress sauce.
Time and servings
2 hrsTotal time
2Servings
1 hrPrep time
1 hrCooking time
Ingredients
- 1 fennel bulb, roughly chopped
- ½ tsp fennel seeds
- 3 tarragon sprigs
- 35g parsley
- 1 lemon, juiced
- 3 shallots
- 200ml crisp and zingy white wine
- 1 tsp black peppercorns
- 3 medium free-range eggs
- 1 tsp Dijon mustard
- 2 tsp white wine vinegar
- 20g cornichons, roughly chopped
- 20g capers, roughly chopped
- 50ml cold-pressed rapeseed oil
- 1 tbsp butter
- 50ml M&S vegetable stock
- 160g watercress leaves
- 100ml double cream
- 1 tsp crème fraîche
- 220g M&S Loch Trout fillets
- 300g asparagus, trimmed
- 1 tbsp olive oil, for drizzling
- 450g M&S gastropub mashed potato
Method
Step 1
First, make the poaching liquor. Put the chopped fennel, fennel seeds, 1 tarragon sprig, 15g of the parsley, the juice of ½ the lemon, 2 of the shallots (roughly chopped) 150ml of the white wine and 200ml water into a large pan. Add a few black peppercorns, bring to a simmer, then turn off the heat and leave to infuse.Step 2
To make the sauce gribiche, bring a separate pan of water to a boil and carefully lower in the eggs. Boil for 8 mins, then drain and run under cold water until cool. Peel the eggs, cut them in half and put the yolks into a mixing bowl. Finely dice the egg whites and set aside.Step 3
Add ½ tsp of the Dijon mustard, the remaining lemon juice and the white wine vinegar to the yolks. Add a pinch of salt and pepper and whisk until you have a smooth paste. Slowly drizzle in the rapeseed oil while whisking continuously, until a thick mayonnaise forms. Fold in the cornichons, capers, diced egg whites, 5g of the parsley (finely chopped) and the remaining 2 tarragon sprigs (picked and chopped).Step 4
To make the watercress sauce, melt the butter in a pan over a medium heat. Finely dice the remaining shallot and cook for 3-4 mins until soft. Turn up the heat, add the remaining 50ml white wine and the vegetable stock. Simmer for 5 mins, until reduced by half, then stir in the double cream. Remove from the heat and leave to cool slightly before pouring into a blender with the watercress and the remaining ½ tsp Dijon mustard. Blend until smooth, then stir in the crème fraîche.Step 5
Bring the poaching liquor back to a gentle simmer. Carefully lower in the trout fillets and poach for 6-7 mins, until just cooked through. Remove with a slotted spoon.Step 6
Meanwhile, turn the grill to high. Drizzle the asparagus with olive oil and place on a foil-lined baking tray. Grill for 5-6 mins, until lightly charred.Step 7
Heat the mash according to the pack instructions. Finely chop the remaining 15g parsley and stir it through the mash. To serve, add a spoonful of mash to each plate and top with a poached trout fillet, the grilled asparagus and both sauces.