For the mayonnaise
- STEP 1
For the mayonnaise, bring a pan of water to the boil and have a bowl of iced water ready. Plunge the garlic leaves into the boiling water for 30 secs, then lift out with a slotted spoon and drop into the iced water – this helps to keep the green colour. Leave for a few mins, then pat dry and put in a mini food processor with the egg yolks and mustard. Pulse until finely chopped, then scrape into a big mixing bowl. Pour the oils into a jug.
- STEP 2
Whisk the yolks mixture with an electric whisk. Slowly add the oil, first a drip at a time, then in a steady, thin drizzle – the mixture should thicken and start to look like mayonnaise. If at any point it starts to look greasy, add 1 tbsp cold water and continue whisking until all the oil has been added and you have a thick mayonnaise. Add the vinegar and season with salt and white pepper. Lay cling film directly onto the surface of the mayonnaise so a skin doesn’t form, then chill. Will keep for 3 days in the fridge.
- STEP 3
Heat oven to 180C/160C fan/gas 4. Put a large sheet of baking parchment in a large roasting tin and arrange the asparagus in a line that’s long enough for the salmon to sit on. Season, put the salmon on top and scatter over the lemon zest. Thinly slice the remaining lemon and put the slices on top of the salmon with the butter. Pour over the lemon juice and season. Bring the sides of the parchment up and over the salmon and scrunch together to seal, creating a tent over the fish. Bake in the oven for 30 mins.
- STEP 4
Bring the roasting tin to the table, open the parcel, and serve with a bowl of wild garlic mayonnaise and some new potatoes on the side.