Custards, creams & meringues
Skyr
skyr · A traditional Icelandic cultured dairy product made by inoculating pasteurised skim milk with a mesophilic skyr culture and a small amount of rennet, then incubating until the milk coagulates into a thick curd. The curd is gently broken and hung in cloth to drain the whey (mysa) for many hours, producing an extraordinarily dense, protein-rich, mildly tangy base that functions as a reusable dairy foundation for both sweet custards, cream desserts, and savory applications.
The formula
4 L skim milk → ~1 kg skyr (≈4:1 by mass)
The bulk loss is whey (mysa); curd-to-whey split depends on straining time and cloth weave.
Identity
- Strained mesophilic cultured dairy of Icelandic origin, distinct from yogurt in that skim milk, not whole milk, is used and rennet is added alongside the culture.
- Far higher protein density than yogurt (roughly 12–15%) because substantially more liquid is removed by cloth hanging.
- Tangy lactic-acid flavour dominates; sweetness is absent unless added by the cook.
- Spoon-thick to sliceable texture depending on residual whey; the curd is opaque and matte white.
- Whey by-product (mysa) is itself a legitimate traditional Icelandic beverage, hot or cold.
- Functions as a neutral-tangy base: it accepts vanilla, sugar, fruit, chocolate, herbs, or salt without losing its structural identity.
Ingredients
| Base | Pasteurised skim milk | Tradition and current practice both call for skim; fat would inhibit the characteristic dense texture. |
| Culture | Skyr mesophilic culture (lactic acid bacteria blend carried over from a previous batch or commercial starter) | Provides acid coagulation and the signature tang. |
| Binder | Rennet (a few drops) | Promotes a clean, firm gel so the curd hangs without slipping through the cloth. |
| Enrichment | Residual mysa / whey retained in the curd | A small fraction of whey is retained to keep the curd moist; the rest drips away as by-product. |
Method
- 1Pasteurise skim milk, then cool to around 32–38 °C.Kills competing organisms and brings the milk to the temperature where the mesophilic skyr culture will acidify cleanly.
- 2Inoculate with a small portion of mature skyr culture and stir gently.Introduces the right lactic bacteria and seeds the future batch; live starter drives acidification.
- 3Add a few drops of rennet and stir to disperse.Rennet forms a fine protein network so the curd sets firm rather than soft, which is what allows cloth-straining without losing solids.
- 4Incubate covered until the milk is fully set — several hours at culturing temperature until the gel breaks cleanly into thick curds and whey.Acid from the culture plus rennet coagulation creates a single mass of curd floating in greenish whey.
- 5Skim the curd into muslin or fine cotton and hang over a vessel to drain.Cloth hanging removes the bulk of the whey passively, concentrating solids and flavour without mechanical squeezing that would drive out fat and break texture.
- 6Collect the thick drained curd (the skyr); reserve the dripping whey as mysa.Yields the finished reusable base; whey becomes a usable by-product rather than waste.
Techniques that matter
Hanging-strain through cloth
Passive gravity draining concentrates protein and flavour without shearing the delicate gel — the defining technique versus pressed or centrifuged yogurts.
Live-culture carryover
Traditional skyr-making keeps a portion of the previous batch as inoculum, which is why skyr cultures reliably produce the same tart profile across generations.
Skim-milk choice
Using skim rather than whole milk lets the culture produce a denser, leaner curd — fat would soften the gel and slow whey release.
Variations & derivatives
Skyr me vanillu og rjmaIceland
Plain skyr folded with vanilla and whipped cream for a festive dessert base.
Skyr-grautur (Skyr Pudding)Iceland
Skyr thickened further with a vanilla custard sauce to form a spoonable pudding base.
Skyr custard toast baseModern café / international
Skyr blended with egg yolks and sweetener to function as a pourable custard baked on bread wells.
Skyr pudding with chocolateIceland
Skyr combined with chocolate and custard sauce for a layered chilled dessert base.
Used in these dishes
Substitutions
- Greek yogurt → Skyr — Strain Greek yogurt overnight in cheesecloth to approximate skyr thickness; flavour will be less tangy and slightly higher in fat.
- Labneh (strained sheep/yogurt) → Skyr — Suitable in sweet custards; higher fat and saltier profile, so reduce added salt elsewhere.
- Quark → Skyr — Similar protein-rich curd but milder acidity; works as a structural swap, not as a flavour swap.
- Plain thick coconut yogurt → Skyr — Works for dairy-free custards only; coconut fat changes texture, so it cannot be used where skyr's lean curd defines the dish.changes result
Troubleshooting
Final skyr is thin or weepy
Under-straining, cloth too open, or insufficient rennet leaving the gel too fragile to release whey. → Re-hang for several more hours in finer cloth; for next batch, ensure rennet is dispersed and incubation is complete before hanging.
Skyr is harshly sour
Over-acidification — incubation too long or too warm, or too-large a starter ratio. → Shorten incubation, lower the temperature slightly, and reduce the carryover culture by a spoonful for the next batch.
Grainy or chalky texture
Rough handling of the gel or excessive rennet causing curds to shatter. → Stir or break the curd as little as possible before hanging, and dose rennet sparingly (a few drops per litre).
Curds slip through the cloth
Rennet too weak or fabric weave too coarse, so the gel never fully sets into a self-supporting mass. → Switch to a finer woven muslin and confirm rennet freshness with a small milk test before the full batch.