Place the clam juice, lobster bisque, and water into a saucepan and bring to a simmer.
In a separate large skillet, (3 quart), heat the olive oil on medium-low heat. Add the chopped onion and cook until softened, 4 to 5 minutes.
Increase the heat on the stove to medium, add the rice to the pan, stir to coat, and cook for 1 minute. Then add the wine and stir until the wine is absorbed.
Add 1 cup of heated broth to the rice and stir constantly until nearly absorbed. Then, continue to add the broth in increments of approximately 1/2 cup at a time while stirring until nearly absorbed. Start tasting the rice after about 20 minutes of cooking time. The rice is done when it is al dente, thick, and creamy. Add salt and pepper to your liking.
Remove the pan from the heat and stir in the mascarpone cheese and the cooked seafood. Garnish the risotto with chopped parsley and drizzle with fresh lemon juice. As an alternative, serve the seafood on top of the plated risotto.
*See the recipe notes below. While the rice is cooking, melt the butter in a large skillet on medium heat, adding the minced shallot, and cook for 2 minutes. Then, toss in the shrimp and scallops and cook until they are opaque and cooked through, 3 to 4 minutes.