Adapted from "Joanne Weir's Cooking Class" on PBS. She did not give quantities in the episode, and I haven't made it yet, so these are best guess amounts. I will adjust when I get a chance to cook it.
Peel and devein shrimp. Bring clam juice to a boil and add shrimp shells; reduce to a simmer and cook 10 minutes. Keep warm over very low heat.
Heat 2 T olive oil over medium heat. When shimmering, add shrimp and saute until almost fully cooked, 2-3 minutes. Add 1/2 c white wine and reduce by half, 1-2 minutes. Transfer shrimp and any remaining liquid to a bowl.
Heat 2 T olive oil until shimmering. Add onion and salt and saute until soft and translucent, 5-7 minutes. Add rice and stir until rice is opaque, 2-3 minutes. Add 1/2 c white wine and 2 tbsp lemon juice.
Strain shrimp shells out and discard. Add broth to rice, 1 ladle-full at a time, stirring frequently. When a spoon drawn across the bottom of the pan leaves bare metal, without the risotto sliding in to fill the space, add more broth. It should take 18-20 minutes to add all the broth.
Before adding the final ladle of broth, add shrimp and juices, Parmigiano, lemon zest, remaining lemon juice and butter, along with remaining broth. Stir well, turn off heat, cover pan, and leave undisturbed for 5 minutes. Garnish with parsley before serving.