For the beurre blanc
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
For the asparagus
12 spears fresh asparagus
12 slices prosciutto
1 tbsp olive oil
Peel and roughly 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. Discard the shallot. You can use the sauce immediately or you can keep it for 2-3 hours at warm room temperature without it splitting.
Ttrim the tough, fibrous base.
Make a bundle of three asparagus spears. Wrap the bundles in a slice of prosciutto and roll tightly. Wrap the bundle two more times with two additional pieces of prosciutto. Trim the ends of both bundles so they're the same size.
Heat the olive oil in a large frying pan and fry the prosciutto-wrapped asparagus bundles until the prosciutto is lightly browned, about 6-8 minutes, turning over several times to ensure even cooking.
Squeeze the lemon juice into the beurre blanc sauce.
Serve the asparagus bundles on a plate with the sauce drizzled over and around, with extra sauce on the side.