Use a pair of shears to snip down
the outer, curved side of the prawns,
then peel off the shell and tail,
reserving them. Put the prawns on a
small plate or in a container, cover
and chill until ready to use.
Lightly crush the coriander and
cumin seeds. Quarter the onion and
cut out the root. Heat a medium 2.75
litre saucepan over medium– high.
Add 1 tablespoon of oil, the prawn
shells and tails, the coriander and
cumin and one-quarter of the onion.
(Hang on to the other 3 wedges of
onion.) Cook, stirring, until the shells
are bright red and the spices are
popping, 2–3 minutes. Carefully pour
in 2 litres water (it
will sputter when it hits the pan) and
season with salt and pepper. Bring
to a simmer, then lower the heat and
simmer gently until the stock is
lightly flavoured, about 30 minutes.
Strain the stock into a container,
discarding solids, and set aside.
Meanwhile, roughly chop the
jalapeño and place it in a blender
with the coriander, anchovies, 2
garlic cloves and 1 tablespoon oil.
Remove the fennel fronds from the
bulb and roughly chop half of them
(reserve the remainder for serving);
add to the blender. Season with salt
and pepper.
Pour in 250ml cold water and
blend on high until smooth. Thinly
slice remaining onion quarters and
garlic cloves. Halve and thinly slice
the fennel bulb. Scrub the potatoes.
Heat the remaining oil in a medium
pot over medium–high. Add the
onion, garlic and fennel, stir and
season with salt and pepper. Lower
the heat to medium, partially cover
the pot and cook, stirring
occasionally, until the vegetables are
very soft and starting to brown, 10–12
minutes. Add the stock and bring to
a simmer. Add the potatoes; season
with salt and pepper. Lower the heat
to medium–low, partially cover the
pot and simmer gently until the
potatoes are tender, 16–18 minutes.
Meanwhile, cut the cod into 5 cm
pieces. Stir the jalapeño-coriander
purée into the stew. Add the cod
and prawns and reduce the heat to
low. Cover the pot and cook very
gently just until the fish and prawns
are cooked through, 2–3 minutes.
Serve the stew topped with a
squeeze of lime juice and some
reserved fennel fronds.