An easy alternative uses cooked lasagne noodles cut into squares.

LOBSTER SAUCE
2 live 1 1/4- to 1½-pound lobsters

2 tablespoons olive oil
1 1/3 cups finely chopped shallots
1 cup chopped fennel bulb
3 large garlic cloves, chopped
1/4 cup Madeira
4 teaspoons tomato paste
3 cups chicken stock or canned low-salt broth

1 tablespoon butter, room temperature
1 tablespoon all purpose flour
1/2 cup whipping cream

FILLING
1/3 cup lentils
2 tablespoons (1/4 stick) butter
2 medium leeks (white and pale green parts only), thinly sliced
6 ounces crabmeat

6 lasagne noodles
2 tablespoons chopped fresh cilantro

FOR SAUCE: Boil lobsters in pot of boiling water 8 minutes. Transfer to bowl of ice water; cool. Drain. Working over large bowl to collect juices, remove claws and tails. Using knife, cut tails into 2-inch-wide pieces. Remove meat. Crack claws; remove meat. Cut bodies in half. Transfer shells and bodies to bowl with juices. Slice meat; place in small bowl. Chill.

Heat oil in large Dutch oven over medium-high heat. Add shallots, fennel and garlic; sauté 8 minutes. Add Madeira and tomato paste; bring to boil. Add stock, lobster shells and any juices; bring to boil. Reduce heat; simmer until reduced to 2½ cups, about 30 minutes.

Strain liquid into saucepan, pressing on shells. Mix butter and flour in bowl. Add to liquid. Bring to boil, whisking often. Add cream; simmer until reduced to sauce consistency, about 8 minutes.

FOR FILLING: Cook lentils in medium saucepan of simmering water until tender, about 20 minutes. Drain. Melt butter in large skillet over medium heat. Add leeks; sauté until tender, about 15 minutes. Add lentils, lobster meat, crabmeat and 1/2 cup lobster sauce.

Cook pasta in pot of boiling salted water until just tender. Drain. Cut each noodle crosswise into 4 pieces. Divide half of pasta among 6 shallow bowls. Rewarm filling, mix in cilantro and spoon over pasta. Top with remaining pasta. Bring sauce to simmer. Spoon over pasta.