Step 1 Pour stock into a medium saucepan with 2 cups water and bring to the boil. Reduce heat to low and keep at a gentle simmer.
Step 2 Heat half of the olive oil in a large heavy-based saucepan set over high heat. Cook mushrooms, stirring, for 3–4 minutes, or until golden; remove from pan and set aside. Add remaining olive oil, onion and celery; cook, stirring occasionally, for 5 minutes, or until vegies are soft. Add garlic and ginger; cook, stirring, for 1 more minute.
Step 3 Add rice and cook, stirring, until rice is evenly coated in oil. Add dry sherry and simmer for 30 seconds. Return half of the mushrooms to pan, reserving remaining mushrooms, and start adding stock, 1 ladleful at a time. Cook, stirring, for 5 minutes, or until stock has almost completely evaporated, before adding the next ladleful. (Adding all of the stock takes about 20 minutes.)
Step 4 Meanwhile, spray a large non-stick frying pan with olive oil and set over high heat. Cook prawns, in batches, for 2 minutes, or until pink and cooked through. Remove from pan and set aside.
Step 5 Finish adding stock and check rice is tender. Add remaining mushrooms, reserved prawns and snow peas; stir to combine. Remove risotto from heat; cover. Leave to stand for 2–3 minutes, then serve immediately.