2 banana shallots or 4 small shallots
100ml dry white wine
250g unsalted cutter, cold, cut into 1cm dice
salt and freshly ground black pepper
½ lemon, juice only
Peel and finely chop the shallots. Place them into a heavy-based pan over a medium heat
Add the white wine to the shallots, turn up the heat to high and simmer rapidly until the volume of liquid is reduced by 2/3rd, about 2-3 minutes. Reduce the heat to low. The liquid should be barely simmering.
Add the pieces of cold butter to the shallot and wine reduction a small amount at a time, whisking thoroughly with a balloon whisk as you go.
Continue adding the butter, a small amount at a time, whisking continuously, until all the butter is used up. Don't overheat or the sauce will split. The finished sauce should be thickened and emulsified.
Season to taste.
Strain the sauce through a sieve into a bowl. You can use the sauce immediately or you can keep it for 2-3 hours at warm room temperature without it splitting.
Squeeze the lemon juice into the sauce before serving