Talking food on the phone with my Mum last week, the subject got on to sauces. It turns out that we share a favourite – beurre blanc, a deliciously fatsome emulsion of melted butter suspended in reduced wine infused with herbs and shallot. After putting the phone down, I headed straight for the fridge.
Being fatsome, beurre blanc works best as a sauce for very lean dishes. I steamed trout en papilotte – inside a little bag made from greaseproof paper – in the oven, with more herbs and wine, then spooned the beurre blanc all over it. (I also spooned beurre blanc all over some home-fried potatoes, which are not pictured because only people who do not fear imminent death via clogged arteries should eat beurre blanc spooned all over home-fried potatoes.) It was ludicrously good.
To serve four, you’ll need:
Eight trout fillets
4 bay leaves
4 sprigs tarragon
4 sprigs parsley
4 thin slices of lemon (with skin)
Salt and pepper
225g unsalted butter
1 bay leaf
5 tablespoons white wine
1 tablespoon white wine vinegar
1 teaspoon double cream
Salt and pepper
Make sure the butter is chilled, and preheat the oven to 180° C (350° F).
Cut out four large squares of greaseproof paper and four squares of tinfoil. Lay the pieces of greaseproof on top of the tinfoil squares, and lay a bayleaf, half a sliced shallot, a slice of lemon and a sprig of parsley and tarragon in the middle of each. Place two fillets of trout on top of each pile of herbs and sprinkle with salt and pepper. Sprinkle a couple of tablespoons of wine over the fish and fold the paper and tinfoil over to create a little packet, sealing it tight with the foil. There should be a bit of room for the steam to circulate in each packet, so don’t wrap the fish up too tight. Put all four little packets on a baking sheet and put in the oven for 20 minutes.
As soon as the fish goes in the oven, start making the sauce. Put the wine and vinegar in a heavy-bottomed saucepan with the sliced shallot, the bay leaf and the peppercorns. Bring to a simmer and reduce until there is only 2 tablespoons of liquid left. Sieve the liquid to remove the shallot, bay and peppercorns, and return to the pan off the heat. Get the butter out of the fridge and cut it into cubes about the size of the top joint of your thumb.
Lower the heat, and put the pan back over the low flame. Add a teaspoon of cream to the wine reduction and use a whisk to incorporate it into the liquid. (A note here – adding cream is, strictly speaking, cheating. The cream stabilises the emulsion and will stop your sauce from breaking and splitting. Proper chefs will scoff and tell you that the addition of cream means your sauce is no longer a beurre blanc. Scoff right back at them, but make sure you take your time over it so that by the time they return to their own, cream-free beurre blanc pans, their own sauce will have split.) Whisking vigorously, add the butter to the pan, three cubes at a time. When they are half-melted, add another three, still whisking hard. Repeat until all the butter is incorporated and remove from the heat. Taste for seasoning and add salt and pepper.
The fish should be ready at around the same time you finish the sauce; if the timer goes before you’ve finished the sauce, don’t worry about it. The fish won’t mind an extra five minutes in the oven.
Some people like to open the little parcels of fish at the table – the burst of fragrant steam from the punctured parcel is a fantastic opening to the meal. Spoon over the beurre blanc and some fresh parsley, and serve plenty of new potatoes or mash to help you soak up all the delicious sauce.