Hey {{first_name|there}},
Welcome to number three of open kitchen. Last week ended with whisking cold butter into a sauce. Which leaves one obvious question: into what sauce exactly? hahah
So this week we go one step back, to where every restaurant sauce actually starts: a proper stock, and reducing it. Just the basics, tip of the iceberg, but it's the part that makes a restaurant sauce taste so different from the one at home.
Why it matters
You know that sauce at a restaurant that's glossy, a bit sticky on your lips, and tastes like way more than it should? That's almost never a secret ingredient. It's a stock someone made properly and then reduced.
Stock gives you two things: flavour and body. The body comes from gelatin, which comes out of the bones, heads and skin while they cook. Water can't give you that, and neither can most stock cubes.
Reducing is just letting the water cook off. The flavour and the gelatin stay behind and get more concentrated. Reduce a good stock by half and you have a sauce base. Keep going and you have a sauce.
The stock
This week it's fish stock, because it's the fastest one there is. A veal stock takes the whole day, fish is done in half an hour. The recipe is below, these are the rules that matter:
Clean the bones first. Cut out the gills and rinse off all the blood under cold water. Both make your stock bitter and grey.
Start cold. Everything goes into cold liquid and comes up to temperature slowly. The impurities rise to the top as foam, and you skim them off.
Never let it boil. Boiling smashes the fat and all the little bits into the liquid and you end up with cloudy, greasy stock. A few lazy bubbles, that's it.
20 to 30 minutes, not more. Fish bones are thin and give their flavour fast. Cook them longer and it gets bitter and chalky instead of better.
Cook stock in stock if you can. Leftover fish stock from last time instead of water gives you double the flavour. Mine was hamachi stock. No old stock? A bit of store-bought or bouillon works, or just use water and reduce a bit more at the end.
Don't salt it. You're going to reduce it, and like we said in number one, the salt concentrates with everything else.
Reducing it
Strain first, then reduce. Once the bones are out the stock can take a proper simmer. With the bones still in, all you'd be reducing is bitterness.
Use a wide pan. More surface means it reduces faster, and the faster it goes, the fresher it tastes. Keep skimming whatever comes up.
Use the spoon test. Dip a spoon in and run your finger across the back. If the line stays clean, it's a sauce. Keep going and it becomes a glace: sticky, almost syrupy, and it sets like jelly in the fridge. One spoon of that in a sauce does a lot.
Season at the very end. Taste it once it's where you want it, then salt and a few drops of lemon.
Finish it with butter. Off the heat, whisk in a few cubes of cold butter (monter au beurre from last week). Reduced fish stock, butter, a squeeze of lemon, and you have a proper sauce for fish in two minutes.
What to look out for
Don't boil the kombu. Take it out right before the stock starts to simmer. Boiled kombu goes slimy and bitter.
The end of a reduction goes fast. The first half takes ages and the last bit takes a minute. Glace and burnt glue are closer than you think, and burnt is bitter with no way back. Stay with it at the end.
Store-bought stock won't reduce like homemade. Most have barely any gelatin and are already salted, so reduce them hard and you get salty water instead of a sauce.
Freeze it in portions. Cool your stock fast and freeze it in containers, or freeze the reduced version in ice cube trays. One or two cubes and you have a sauce for two.
Want me to keep going with sauces?
Try it this week
Take 500 ml of stock (homemade or store-bought) and reduce it in a wide pan. Every time it loses about half, taste it and do the spoon test. You'll taste it go from soup to sauce in one pan. And if you try it with store-bought, you'll also find out why I keep going on about homemade hahah.
Recipe of the week: fish stock
A basic fish stock, the way it's done in a three-star kitchen. It makes about 1.5 litres. A bit of Japan in there too, and that's what makes people ask what's in it.
1.5 kg white fish bones and heads (turbot, sole, brill or hake), gills removed
1 white onion, sliced
2 celery stalks, sliced
1 leek, white part, sliced
10 g Hokkaido kombu (a piece about the size of your hand)
4 dried shiitake mushrooms
a few sprigs of tarragon
a small bunch of parsley (the stalks are perfect)
2 bay leaves
1 tsp peppercorns
2 litres of leftover fish stock, or water with a splash of store-bought fish stock or bouillon, or just water
Rinse the bones under cold water until there's no more blood. Put the bones, onion, celery, leek, kombu and shiitake in a pot and cover with the cold stock or water. Bring it up slowly on medium-low heat and pull the kombu out just before it starts to simmer. Skim off the foam, keep it at a gentle simmer for 20 minutes, then add the tarragon, parsley, bay leaves and peppercorns for 10 more. Take it off the heat, let it rest 10 minutes so everything settles, then ladle it through a fine sieve (or a sieve lined with a cloth). Cool it fast. Used only water? Reduce it a bit further to get the same depth.
One thing to know: don't press the bones in the sieve. It feels like you're getting more out, but you're mostly pushing cloudiness and bitterness through.
Why it works
Kombu is loaded with glutamate, dried shiitake with guanylate, and fish with inosinate. All three are umami, and together they don't just add up, they multiply. That's the whole trick behind Japanese dashi, and it's why this stock tastes so deep after only half an hour. The body comes from the gelatin in the heads and skin, which comes out fast in fish. That's also why you stop at 30 minutes: by then you have everything good, and anything after that is bitterness from the bones.
Until next Wednesday
That's it for number three. If you make the stock, reduce some, do the spoon test and send me a picture. I genuinely wanna see it. Questions about stock or anything else? Just hit reply, I read everything myself.
See you next Wednesday ;)
P.S. Know someone who still boils their stock for four hours "for extra flavour"? Forward them this one, the fish will thank you. They can subscribe here so the next one lands in their inbox too.