Fill a pot with halfway with water

Add salt to taste

Add <quantity>250<unit>g</unit></quantity> of potatoes and cook over medium heat until still intact, but easily pierced with a fork. Remove them from the hot water

Trim and peel <quantity>1</quantity> small horseradish root

Finely grate <quantity>¼<unit>cup</unit></quantity> of horseradish into a bowl with <quantity>2/3<unit>cup</unit></quantity> of crème fraîche

Season with salt to taste

Mix until everything is combined

Add the juice of <quantity>1</quantity> lemon into the bowl

Add <quantity>50<unit>ml</unit></quantity> of water and mix until thoroughly combined. The Horseradish Sauce is ready

Cut off the tip of the stem of <quantity>1<unit>head</unit></quantity> of gem lettuce. Cut it in half

Trim <quantity>2</quantity> red spring onions. Cut the onions in half and remove the upper tip of the stems

Cut <quantity>8<unit>stalks</unit></quantity> of broccolini in the middle, separating the flower from the stem

Add salt to taste to a skillet over medium-high heat

Add the vegetables, with the lettuce and onions cut-side down

Sear until browned. Transfer to a tray

Cut <quantity>1</quantity> cucumber in half. Chop it while moving the cucumber to cut diagonal chunks

Roughly chop the potatoes into chunks

Quarter each half of lettuce and halve the onions pieces

Arrange the vegetables on a serving plate

Remove the skin of <quantity>1</quantity> smoked mackerel. Pull the flesh off the bones and break it into large pieces over the vegetables

Dress with the horseradish sauce to taste

Garnish with some watercress and picked dill to taste. The Smoked Mackerel Salad is ready

Enjoy making this salad when you have friends coming over! It is perfect for sharing!