For the asparagus:
Cut asparagus into halves, lengthwise. Slice halves in thirds and then cut in pieces, each 4 cm long. Sauté asparagus in butter, season them, add poultry broth and cook. Keep asparagus broth for further processing. Mix leek with asparagus and season it.
For the sweetpotatoes:
Season sweetpotatoes with sea salt and drizzle with olive oil. Wrap in aluminum foil and cook in the oven at 160 °C for ca. 40 minutes. Peel and slice in evenly pieces and sauté in butter with lime peel and Piment d’Espelette.
Dry cooked sweetpotato peel in the oven at 80 °C overnight and roast it in a pan until it is crunchy. Afterwards season the chips with salt.
For the lemon foam:
Put all ingredients in a jar and froth it with a mixer until you have an emulsion that can be put in the siphon. Close siphon and put in 70 °C warm bath. Shake from time to time so that the egg does not clot.
Spread asparagus, leek and sweetpotato on the plate, drizzle with lime foam and scatter leek slices on top to finish the dish. Garnish plate with your sweetpotato chips.