Twist the heads from the prawns, then
peel away the legs and shells, but leave
the tails intact. Devein each prawn. Fry the shells in 1 tbsp
oil for 5 mins, until dark pink and golden
in patches. Add the wine, boil down by
two thirds, then pour in the stock. Strain
into a jug, discarding the shells.
Heat the rest of the oil in a deep frying
pan or casserole. Add the fennel, onion
and garlic, season, then cover and
gently cook for 10 mins until softened.
Meanwhile, peel the potato and cut into
2cm-ish chunks. Put into a pan of cold
water, bring to the boil and cook for 5 mins
until almost tender. Drain in a colander.
Peel a strip of zest from the orange.
Put the zest, star anise, bay and ½ tsp
harissa into the pan. Fry gently, uncovered,
for 5-10 mins, until the vegetables are
soft, sweet and golden.
Stir in the tomato purée, cook for 2 mins,
then add the tomatoes and stock. Simmer
for 10 mins until the sauce thickens
slightly. Season to taste. The sauce can
be made ahead, then reheated later in
the day. Meantime, scrub the mussels or
clams and pull away any stringy beards.
Any that are open should be tapped
sharply on the worktop – if they don’t
close after a few seconds, discard them.
Reheat the sauce if necessary, then stir
the potato, chunks of fish and prawns
very gently into the stew. Bring back to
the boil, then cover and gently simmer
for 3 mins. Scatter the mussels or clams
over the stew, then cover and cook for
2 mins more or until the shells have
opened wide. Discard any that remain
closed. The chunks of fish should flake
easily and the prawns should be pink
through. Scatter with the thyme leaves.
To make the quick rouille, stir the rest
of the harissa through the mayonnaise.
Serve the stew in bowls, topped with
spoonfuls of rouille, which will melt into
the sauce and enrich it. Have some good
bread ready, as you’ll definitely want to
mop up the juices.