Here’s an existential question for you: Why do they put an expiration date on buttermilk? Buttermilk is not an ingredient I work with often, but I happened to have some in my fridge from making biscuits, and while I was wondering how to use it up, I noticed the expiration date had passed. So I started sniffing the buttermilk to see if it had gone bad. The trouble is, buttermilk has already technically gone bad, or soured — that’s what makes it buttermilk.
Luckily, we have the Internet now or I wouldn’t know anything about anything, so in about 60 seconds, I was able to discover that the expiration date on a carton of buttermilk is pretty arbitrary. People reported using buttermilk up to a month after the date had passed and said you should throw it out if it clearly smells rancid or there’s mold growing on it. Eww. No worries there.
But what I made for dinner was wine-poached fish fillets. This is really more of a cooking technique than a recipe, a method for keeping fish moist and infusing it with flavor while it cooks. I used salmon fillets and served it with steamed broccoli and mashed potatoes (ahh, that’s where the buttermilk went!).
The poaching liquid is one part white wine (the same kind you would drink with dinner) and one part chicken stock. How much liquid you need depends on a) the size of your pan and b) the thickness of your fillets. You want the liquid to come up to two-thirds of the height of the fish.
Add to the liquid: herb sprigs (I used rosemary); whole peppercorns; sea salt; lemon slices; whole garlic, sliced thickly; and thickly sliced shallot. Feel free to vary as suits you. Cover and heat over medium-low to the point where the liquid is just bubbling. Simmer until the fish is fully cooked, which again depends on the thickness of your fillets. Fully cooked fish will be opaque in the middle and flake easily under a fork. Spoon a little of the poaching liquid over the fish to serve and garnish with more fresh herbs, a little butter and lemon wedges for squeezing.