Ymer substitutes

Ordinary unsweetened set yogurt, loosened slightly so it pours like ymer instead of standing up like a scoop of Greek yogurt.

Best for

breakfast bowls with ymerdrys, baking and quick breads, cold sauces and dressings, marinades, stirring into muesli

The closest thing on an American or British shelf. Yogurt is cultured warm with thermophilic bacteria, so it tastes a touch sharper and cleaner than ymer, which is cultured at room temperature and comes out milder and more buttery. In a breakfast bowl that difference is small and the brown-sugar-and-rye ymerdrys topping covers it entirely. In baking it makes no difference at all. Use full fat: low-fat yogurt turns the bowl watery and chalky.

Strained fresh dairy that matches ymer's unusual selling point, which is high protein at moderate fat.

Best for

breakfast bowls, high-protein swaps, dips and spreads, cheesecake and dessert fillings

Nutritionally this is the nearest match, since ymer is essentially milk with some whey removed and both skyr and quark are made the same way. Straight from the tub they are much too stiff, so thin them until a spoonful sags. Skyr is noticeably more acidic than ymer and quark is milder and slightly grainy, so quark plus a splash of milk lands closest of all. Whisk properly or you get lumps that will not disappear.

Cultured pourable milk with the same lactic tang as ymer but nowhere near the body.

Best for

pancakes and waffles, cakes and muffins, soda bread, salad dressings, cold soups

For anything baked this is a straight swap, because the only jobs ymer is doing in a batter are supplying acid to react with baking soda and supplying liquid, and buttermilk does both identically. Where it fails is the breakfast bowl: buttermilk is thin enough to drink, so it will not hold a topping and will taste sharper and saltier than ymer. If you need it thicker for a cold dish, whisk in a tablespoon of sour cream per cup.

Fermented milk drink cultured with both bacteria and yeasts, so it has a faint fizz and a yeasty edge ymer does not.

Best for

drinking and smoothies, baking, marinades, pouring over cereal

Sourer and livelier than ymer, with a champagne-like prickle and a slight bready aroma. Fine in batters, good over muesli, and honestly quite pleasant in a bowl, but it reads as a different product rather than a stand-in. If the recipe is a dessert or a mild sauce, cut the kefir with plain yogurt so the funk does not dominate.

A rich, low-acid cultured cream diluted back down to something ymer-like in thickness.

Best for

cold sauces, desserts and fruit compotes, creamy soups finished off the heat

Gets the smooth mouthfeel right but overshoots badly on fat, so the result tastes distinctly richer and less refreshing than ymer, which is only around three or four percent fat. The tang is milder too. Use it when ymer is playing a sauce role and you want luxury; do not use it for a breakfast bowl you were eating because it felt light.

The emergency version, which supplies acid and nothing else.

Best for

pancakes, muffins and quick breads, any batter leavened with baking soda

This is a baking-only fix and it is a good one, because the acid does the chemistry ymer was there for. It will not thicken meaningfully and it tastes flatly sour rather than cultured, so it is useless for eating. There is no fermented complexity here at all, and in a plain cake nobody will notice; in a cheesecake or a cold sauce they will.