1. Bring the stock to a gentle simmer in a medium saucepan.
2. Meanwhile, cut calamari hoods down the centre to open out. Score the inside
in a diagonal pattern, then cut into pieces. Shell and devein prawns, leaving tails intact.
3. Heat half the oil in a large, heavy-based pan; cook prawns and calamari over high heat, in batches, until the prawns have just changed colour. Remove from pan.
4. Heat the remaining oil in same large, heavy-based pan; add onion and garlic, cook, stirring, until onion is soft. Add rice and saffron, stir to coat well with onion mixture; cook, stirring for 1 minute. Add wine, simmer, uncovered, until liquid has evaporated. Stir in tomato purée cook, stirring, for 1 minute.
5. Stir in 1/2 cup of the hot stock; cook, stirring, over a medium heat, until the liquid is absorbed. Continue adding stock, 1/2 cup at a time, stirring between each addition, until all but 1/2 cup of the stock has been absorbed (this step should take about 20 minutes). Stir in remaining stock and mussels; cover pan with lid, cook for about 5 minutes or until mussels have opened.
6. Return the prawns and calamari to pan with the rind and parsley; stir in gently.

Not suitable to freeze or microwave.