This one started with an ingredient I almost threw away.
I bought a 200ml tub of crème fraîche with grand plans for salmon rillettes — but life happened, and it sat untouched in my fridge past its expiry date. Three days past, to be exact. Still sealed. It still smelled clean and tangy. No mould, no off-odour.
Here’s the thing about crème fraîche: it’s a cultured product, naturally fermented with live bacteria that give it that signature tang — and those same bacteria act as natural preservers. An unopened, properly refrigerated tub often stays safe a little beyond its best-by date. But this is never a guarantee. Always use your senses — look, smell, and check the texture before you decide.
And since butter has traditionally been made from fermented or soured cream, it made perfect sense to churn this crème fraîche into something worth spreading: a small-batch fermented butter with shio kombu for a quiet hit of umami saltiness.
Singapore’s heat meant I kept everything ice-cold throughout — ice packs under and around the food processor were a lifesaver. The whole process took about 30 minutes from start to finish, and the yield was a satisfying ~100g of butter from just one tub.
Kombu Butter
Equipment
- Food processor or blender
Ingredients
- 200 ml crème fraîche sealed, unopened
- 8 g shio kombu finely chopped
- 1 pinch smoked salt optional
Instructions
- Place crème fraîche in a food processor or blender and beat on high.
- Check the texture periodically — the cream will first whip, then begin to look grainy.
- After approximately 20 minutes, the mixture will curdle and separate into solid butter and liquid buttermilk.
- Sieve the solids from the buttermilk
- Wash the butter under cold water, changing the water several times until it runs completely clear.
- Add the finely chopped shio kombu and mix well.
- Wrap in cling film or parchment paper and roll into your preferred shape.
- Serve with good bread, or store as directed below (under Notes section)
Notes
- You don't need to wait for expiry — but it's a great way to save. Fresh crème fraîche makes equally delicious butter. This is simply a wonderful way to rescue a forgotten tub rather than send it to the bin. Zero waste, full flavour.
- Unopened vs. opened — this distinction matters enormously. This recipe only works with a sealed, never-opened tub. The moment a container is opened, the clock speeds up dramatically — exposure to air, utensils, and surrounding food all introduce potential contaminants. A previously opened, half-used tub should not be used for this recipe, regardless of how recently it was opened.
- How to check if your crème fraîche is still good. Before using any cream past its printed date, run through these checks: (i) Smell: Fresh crème fraîche has a clean, pleasantly tangy scent. Anything rancid, sulphuric, or otherwise off — discard immediately, no exceptions. (ii) Look: Some liquid separation is completely normal in cultured cream — just stir it back in. What's not normal: unexpected lumpiness, yellowing, or any sign of mould, however small. If mould is present, the entire tub goes in the bin. Mould can produce toxins that persist even through cooking and heating, so there is no salvaging a mouldy tub. (iii) Texture: Should be thick and smooth, consistent with how it looked when first purchased.
- Wash your butter thoroughly — don't skip this. This step is critical for both flavour and shelf life. Residual buttermilk left in the butter turns rancid quickly and will ruin your entire batch from within. Wash under cold water, pressing and kneading the butter until the water runs completely clear. The more thorough your wash, the longer your butter will keep and the cleaner it will taste.
- Storage — be conservative, be safe. This butter contains no preservatives, includes organic matter from the shio kombu, and was made from cream that was already near the end of its date. That means the shelf life is shorter than a standard compound butter. Here's what I recommend: (i) Refrigerator (tightly wrapped)5–7 days, (ii) Freezer (wrap tightly, label with date)Up to 1 month (iii) Room temperature, not recommended.
- My advice: freeze half immediately when shaping. Don't wait to see if you'll finish it. In Singapore's heat and humidity, the fridge is the bare minimum — and the freezer is your best friend for preserving homemade dairy without preservatives. When in doubt, freeze first.
- Shio kombu is optional. Leave it out and you have a pure fermented butter — equally wonderful. Other lovely additions: flaky sea salt, fresh thyme, lemon zest, or a small spoonful of white miso.
- A note for those who are more vulnerable. If you are pregnant, elderly, very young, or immunocompromised, the safer call is always to use cream well within its date. When in doubt, throw it out — a tub of crème fraîche is never worth the risk.
