The day before serving, make the broth. Place the water, sliced onions, salt and sugar in a large sous-vide bag and cook in a pan of simmering water for about 30 minutes until the onions are completely soft.
Once cooked, empty into a bucket. Add the pine needles and bonito while warm, then cover with clingfilm.
Let cool to room temperature then add remaining ingredients. Leave to infuse overnight.
Pass through a chinois sieve into a bowl and set over an ice bath. Place a serving jug in the freezer.
Blanch the perilla and baby spinach for 30 seconds in rapidly boiling salted water in batches, about 30 g per litre of water, then refresh in ice water.
Drain very well and squeeze out all the water until completely dry.
Blend with the salt and oil in a Vita-prep until bright green and steaming hot.
Strain through a double muslin or J-cloth set over a bowl.
Slice the kohlrabi to 1.5 mm thick slices, then season in a bowl. Sous-vide for 30 minutes until tender. Let rest for 20 minutes, then strain.
Mix all the ingredients together in a bowl and set aside.
Place 1 tsp of the pear filling in the centre of each kohlrabi slice then pinch to seal like a wonton. Repeat with the remaining kohlrabi then sprinkle 3 fennel seeds over each parcel.
In a serving bowl, place the dumplings in a circle and top each with a pluche of dressed chickweed.
Remove the jug from the freezer and fill halfway with with pine broth. Pour the broth over the dumplings and add 2 pipettes of perilla oil.