Place the lobsters in a large pot of boiling salted water and cook until cooked through, about 8 to 10 minutes. Remove and drain in a colander. Rinse under cold running water and drain. When cool enough to handle, remove the tail meat, and chop into 1/2-inch pieces. Remove the claw meat and set aside whole.

In a large, heavy saucepan, bring the stock to a simmer. Remove from the heat, cover and keep warm until needed.

In a heavy pot, heat the oil and butter over medium-high heat. Add the leeks and cook, stirring, until begin to soften, about 5 minutes. Add the corn, garlic, salt and pepper, and cook, stirring, until the leeks are soft but not brown and the corn is tender, about 3 minutes. Add the rice and cook, stirring, for 1 minute. Add the wine and simmer, stirring, until absorbed, about 2 minutes. Add the hot stock 1/2 cup at a time, and cook, stirring constantly, until each addition of stock is nearly completely absorbed. Continue until all of the stock has been added and the risotto is creamy. During the last addition of the stock, add the mussels and cook until they open and the risotto is at the right consistency. (It will take about 20 to 25 minutes to add all of the stock and for the risotto to reach the right consistency.) Stir in the cream, oysters and reserved lobster tail meat and cook for 2 minutes. Season, to taste, with salt and pepper.

Divide the risotto among 4 serving plates. Garnish each with 1 lobster claw and 1 tablespoon of dulse. Arrange 2 chive stalks across each bowl and serve.