Scrub the celeriac thoroughly with a clean sponge under running hot water, and then place it in a roasting pan with lots of coarse salt.
Place the roasting pan in the oven at 150 degrees Celsius (302 degrees Fahrenheit) for about 3 hours. Remove and cool, ideally until the next day.
Toast sesame seeds, pistachios, spices, and flaked salt in a dry pan for a couple of minutes.
Place in a food processor and blend to a coarse consistency.
Brown the butter in a small pot and remove from heat.
Brush the salt off the celeriac and peel it with a knife.
Cut into smaller pieces and place the celeriac in a food processor along with the mascarpone and lemon juice.
Process for a couple of minutes until smooth, and gradually add the browned butter.
Season with salt and pepper, and place the cream in a piping bag.
Place the parsley in boiling salted water for 30 seconds.
Strain and then cool it in ice water.
Squeeze the water out of the parsley and blend to a fine consistency with olive oil.
Pipe the celeriac cream into small glass bowls and top with pistachio dukkah and parsley oil, possibly in a pipette.
Serve with crispy grissini or toasted bread.
Keep the display on
Notes
TIP: Instead of piping into bowls, place on toasted bread and use as a spread. Use almonds or hazelnuts instead of pistachios and strained 10% yogurt instead of mascarpone.