Separate the lobster meat from the shells (reserve shells for stock). Chop the meat into 1/2 inch pieces, place in a bowl and and keep in the refrigerator until needed. If using shrimp, shell them (reserve shells for stock), cut into 1/2 inch pieces (maybe leave one to 2 whole for presentation if you want) and place in a separate bowl from the lobster. Set aside in refrigerator.
Rinse the reserved lobster and shrimp shells, including the heads, of any residue. Place all the shells in a large pot and add 3 quarts of water, peppercorns, bay leaf, and leek. Bring to a boil over high heat, then reduce the heat to medium low and simmer for 1 hour. Strain the broth through a fine-mesh strainer set over a medium saucepan. Set the strained broth over low heat and keep it at a bare simmer.
In a large wide pot or Dutch oven, heat the oil and 2 tablespoons of the butter over medium heat until shimmering. Add the shallot and a large pinch each of salt and pepper and cook, stirring often, until the shallot is translucent, about 5 minutes.
Add the rice and cook, stirring, until the kernels start to crackle, about 1 to 2 minutes. Pour in the wine and stir constantly, until all of the liquid has been absorbed, about 2 to 4 minutes. Pour a ladleful of the simmering lobster broth over the rice. Let simmer, stirring constantly, until the rice absorbs the liquid. Continue adding the broth, stirring and letting it absorb, until the rice is al dente, about 20 to 25 minutes (you may not need all of the broth, but if you run out, use hot water or chicken stock). Taste as you go for doneness, seasoning with salt and pepper as needed.
When the rice is almost done, remove from heat and stir in peas and raw shrimp (if using). Cook for 5-7 minutes until shrimp are opaque and just cooked through. Then stir the reserved lobster meat, Parmesan, butter (if desired), chives, lemon zest, and lemon juice. Taste and season with more salt, pepper, Parmesan, and lemon juice as needed. Just before serving, loosen the risotto to the desired consistency with a little more broth or hot water and serve immediately. Drizzle each serving with olive oil.