Kartoffelsuppe

Ingredients

Equipment Needed

• •Heavy-bottomed pot, 4 litre
• •Stick blender or upright blender
• •Sharp chef's knife
• •Cutting board
• •Ladle

Instructions

1. 1

   Clean the leeks

   Slice the leeks in half lengthwise first, then rinse each half under cold running water, fanning the layers open with your thumb. Leeks hide grit deep between their layers, and grit in a blended soup is the one thing you cannot fix later. Once they are clean, slice them across into thin half-moons.

   Use only the white and pale green parts. The dark green tops are tough and bitter and do not belong in a soup you want to taste sweet.
2. 2

   Sweat the alliums

   Melt the butter in a heavy-bottomed pot over a gentle heat. Add the sliced leeks, the chopped onion, and a good pinch of salt. Stir everything through the butter, put the lid on, and let them sweat for ten minutes. You want them soft, translucent, and quietly giving up their sweetness, never browned. Browned leeks taste of caramel and bitterness, and that is not what this soup is asking for. Lift the lid once and stir. If you hear sizzling, the heat is too high. The sound you want is the soft hush of alliums softening in butter.

   The salt at this stage is important. It draws moisture out of the leeks and onion, which is how they cook without color. Without it, they dry out and start to brown before they soften.
3. 3

   Add potatoes and stock

   Add the chopped potatoes, the bay leaf, and the stock. The stock should just cover the potatoes. If you need a splash more water, add it. Bring everything to a gentle simmer, not a hard boil. A hard boil bangs the potatoes against the side of the pot and clouds the soup. Cover with the lid tilted slightly and cook for twenty to twenty-five minutes, until the potatoes are completely tender.

4. 4

   Test the potatoes

   Slide a knife into a piece of potato. It should pass through with no resistance at all. If there is any resistance, keep cooking for a few more minutes. Undercooked potatoes give you a grainy soup, and once it is grainy, it stays grainy. This is the step where patience pays you back.

5. 5

   Blend until velvet

   Fish out the bay leaf and take the pot off the heat. Blend the soup until it is completely smooth and velvety. A stick blender works directly in the pot, which saves you a transfer and a hot mess. If you use an upright blender, work in batches and hold the lid down with a cloth. Hot soup expands, and you learn that rule once and never forget it.

6. 6

   Loosen and season

   Pour in the milk and, if you're using it, the creme fraiche. Blend again until everything comes together into a pale, glossy soup that coats the back of a spoon without clinging to it. Season with salt and white pepper. White pepper belongs here, not black. Black pepper leaves dark specks in a pale soup and its flavor is too sharp. White pepper carries a warmer, rounder heat that stays underneath the potato.

   Taste and adjust. The soup should be rich and rounded, never flat. If it tastes flat, it usually needs salt. If it tastes thin, a little more butter at the end will pull it into focus.
7. 7

   Finish with butter

   Ladle the soup into deep bowls. Drop a small knob of butter onto the surface of each one and let it melt in golden pools. Do not stir it in. That is where half the flavor lives, and it is the difference between soup and this soup. The butter warms, the fat catches the light, and each spoonful carries a little pool of it up to your mouth. Scatter the chives generously over the top and serve immediately with thick slices of rugbrod alongside. Tak for mad.

Chef Tips

• •Use floury potatoes, not waxy. Varieties like King Edward, Maris Piper, or the Danish Bintje break down and give the soup its body. Waxy potatoes stay firm and the texture goes wrong no matter how long you blend.
• •Good stock matters more than you'd think. This soup has almost nowhere to hide, so the stock carries most of the flavor. Homemade chicken stock is best. If you don't have it, use the best you can buy, and avoid anything labelled with words like 'enhanced' or 'rich'. A clean, honest stock is what you want.
• •A small dollop of creme fraiche or cream cheese stirred through at the end is a Jutland trick. It makes the soup rounder and more satisfying without changing its character. I learned it from a farmhouse kitchen outside Viborg one September and I've used it ever since.
• •Rugbrod is not optional alongside this soup. The dark, dense rye bread is how Danes eat it, and the contrast between the soft soup and the heavy, sour bread is half the pleasure. Buy a good one or bake your own.
• •A cold lager or a small glass of snaps is the drink that belongs beside this bowl. Nothing complicated. The soup does the work.

Advance Preparation

• •The soup keeps for three days in the fridge. Reheat it gently over a low flame, stirring often so the bottom does not scorch. Add the finishing butter and chives just before serving, never before storing.
• •It also freezes well for up to two months. Cool completely, then freeze in portions. Defrost overnight in the fridge and reheat gently. If the texture looks a little separated after freezing, a quick whirl with the stick blender brings it back.
• •The leeks and onion can be sweated a few hours ahead and left in the pot off the heat. When you're ready to eat, add the potatoes and stock and carry on from there.

Frequently Asked Questions

Nutrition Information

1 serving (about 550g)