Chill lobster, if necessary. Bring a large pot of salted water to a rapid boil. Place lobster in boiling water and blanch 2-3 minutes.
Using long tongs, remove lobster from pot and plunge in a large bowl or pot of iced water.
Once chilled, split lobster down the centre with a sharp knife. Work on a solid chopping board and cut from the back through to the belly, cut through the head and turn over, repeat on the belly side. Break into half, remove, slice and reserve the tail meat (at this stage the meat need not be cooked through). Break up the shells with the back of the knife or a meat mallet and use it to make the bisque (see below).
Bisque Heat oil in a large saucepan, and add the onion, carrot and celery and fry for 1-2 minutes until tender.
Add lobster shells to saucepan, and cook 1-2 minutes. Add brandy and flamb, then stir in flour and cook for 1-2 minutes. Add soaked saffron and passata and stir constantly for 1 minute.
Add water, white wine, spices and herbs and simmer gently for 25-30 minutes.
Strain bisque through a fine sieve, discard all solids, and return to the heat, reduce slightly.
Risotto In a large pot, combine stock and 2 cups of the bisque, bring to a slow simmer. Meanwhile, in a small saucepan, reduce remaining bisque by half, reserve and keep warm to serve over risotto.
Heat another large, wide (non-reactive) pot. Add olive oil and butter. When butter has just melted, add onions. Cook over a medium heat until soft (4-5 minutes). Add arborio rice, stir to coat. Add wine, stir to combine and evaporate. Reduce heat (to medium-low). Begin adding stock, a ladle or two at a time, just enough to cover rice and keep moist.
Continue adding stock, in intervals, and stirring (20-25 minutes) until rice is "almost done".
As the last of the stock is being absorbed, add lobster meat, peas and extra butter. Stir briefly to combine and season lightly. Remove from heat, cover with lid and rest (5 minutes) before serving.
Serve in large bowls, with a little reduced bisque. Garnish with chopped parsley.