Like so many other memories, this one will date us: Whenever Jackie and I see sorrel in the market we think of our dinner at Troisgros, decades ago when the brothers Jean and Pierre were in the kitchen and the restaurant was right across from the train station in Roanne. One of their signature dishes was a barely cooked slice of salmon with a simple, light wine-and-cream sauce brightened with lots of sorrel and a squeeze of lemon juice.
There was plenty of sorrel in our local farmers’ market the other day, and there were gorgeous little mackerels too; I bought some of each. But I had my doubts about adapting the Troisgros sauce: Cream isn’t the first thing that occurs to me when looking at a filet of mackerel. It probably would have been fine, but I felt I needed a link between the two elements. When I got home, it occurred to me that the link was potatoes. They are perfect with mackerel; cream is perfect with them; and the lemony taste of sorrel (and indeed of lemon) is grand with both.
From the previous week’s market I had a few small elongated potatoes of the Ratte variety, so no further shopping was necessary. The way it worked out was that the boiled potatoes, chunkily sliced while still firm, finished cooking in the slightly simplified sorrel-cream sauce, forming what amounted to a moist potato hash. As we were eating, it occurred to both of us that this could have stood on its own as a side dish for, say, chicken - or as a good potato dinner with nothing more than a few glasses of wine and, if you insist, a salad. In fact, the dish as presented here uses very little fish. Though some people might demand a larger portion, believe me that three ounces (85 g) was entirely sufficient: The crisp skin added texture and the moderately rich mackerel flavor enhanced the potatoes and vice versa. Because the potatoes and sauce can easily be made in larger quantity, it would be a good dish for company so long as you can get over the anxiety that attaches to cooking more than a couple of fish filets simultaneously.
Ingredients for two portions
A generous bunch of sorrel
2 small mackerel fillets, skin on (mine weighed less than 3 oz - 85 g - each)
1 medium shallot
A small lump of butter (20 g or so)
3/4 pound (340 g) firm “waxy” potatoes; I used La Ratte, and they were just about ideal
1/4 cup (60 ml) white wine (you could use dry vermouth)
2/3 cup (160 ml) vegetable stock (plus more if needed)
1/2 cup (120 ml) heavy cream (plus more if needed)
A squeeze of lemon juice (plus more if needed)
Olive oil to pan-fry the fish
Salt and black pepper
Wash the sorrel. Wash it again, and dry it in a salad spinner or a towel. Strip off and discard (or repurpose) the stems. There is no need to cut or tear up the leaves: they will collapse in the hot sauce. Wrap it in a towel and keep it in the fridge (unless you are cooking right away).
Inspect the fish for pin bones by running your finger along the flesh side, head to tail. Remove any bones with whatever tool you have for such purposes: needle-nose pliers or tweezers for instance. Dry the fish well and refrigerate until needed.
Peel the potatoes, rinse them and add them to a saucepan with cold water to cover and enough salt that you can taste it. Cover the pan, bring to the boil, lower the heat and simmer until cooked through but not falling-apart soft; my little rattes took 16 minutes, but larger suitable potatoes such as German butterballs can take 20 minutes or longer.
While the potatoes are simmering, chop the shallot very fine and, over low heat, cook it, sprinkled with salt, in butter until soft. Ideally, use a so-called chef’s pan or a straight-sided sauté pan eight to nine inches (20-23 cm) in diameter. Add the wine, simmer for 30 seconds, then add the stock. Simmer for a minute, then turn off the heat to wait for the potatoes to be done.
When the potatoes are cooked, drain them in a strainer and let excess water evaporate. If using rattes or other elongated potatoes, cut them into slices roughly 3/8 inch (a scant centimeter) thick; halve or quarter larger potatoes lengthwise, then slice each piece crosswise.
Add the potatoes to the shallot-wine-stock mixture, grind some black pepper over them and bring back to the simmer. Cook for a minute or two to allow the potatoes to take on some of the sauce base’s flavor, adding a few tablespoons of additional stock in the unlikely event that things get too dry. Add the cream and bring to the simmer. Add all the sorrel; there will be a huge mound of it, but as you stir it in (I use a rubber spatula) it will collapse to a shadow of its former self. If the mixture seems dry, add a little more cream. Taste for salt and acidity; unless your sorrel is extraordinarily citrusy in flavor, add a squeeze of lemon juice. Taste again and, if necessary, add some more lemon juice.
Now cook the fish: Pat it dry (again) and salt it well. Heat a non-stick skillet over medium-high heat, add a generous film of good olive oil and fry the fish skin side down until the skin is crisp and golden brown and the flesh side warm (not hot) to the touch. For small filets like mine, this could take as little as 90 seconds or two minutes. (You can help ensure that the skin is evenly cooked by pressing lightly with a spatula.) Flip the fish and turn off the heat to gently cook the flesh side without drying it out.
Spoon half of the potato-sorrel mixture onto each of two warmed plates. By this time, the fish will be done and you can place one filet on each plateful of potatoes.
