To make the pesto, roughly chop the wild
garlic and put in a food processor. Blitz for
a few seconds until it is starting to break
down, then add the cheese, hazelnuts and
lemon zest. Blitz again until everything
is ground down to the texture of coarse
breadcrumbs. Add the lemon juice, then
with the motor running, drizzle in olive oil
until you have the texture you like. We prefer
it thick enough to stay on a spoon, so only
add 2–3 tablespoons, but add as much as
you like. Transfer to a sterilised jar if you
want to store it – it will be fine in the fridge
for several weeks.
To make the soup, put the oil and butter in
a large casserole. Heat gently.
When the butter has melted and started
to foam, add the leeks. Cover and leave to
braise for around 10 minutes, stirring and
checking every so often, until the leeks are
just tender.
Pour over the chicken stock, along with
the saffron and its soaking water, the lemon
zest and the tarragon stems. Simmer for 5
minutes, uncovered, then add the chard
leaves, courgettes, broad beans and peas.
Continue to simmer until vegetables are still
al dente and have retained their bright, fresh
green. Add the cooked chicken, if using, and
allow it to heat through in the broth.
Finely chop the tarragon leaves and stir
through the soup. Remove the tarragon
stems from the soup, then serve garnished
with a few wild garlic flowers and leaves,
with the pesto and the black tahini paste on
the side, to be added at the table.