Cook and clean the lobsters, (15 minutes in a pot of boiling water) getting as much meat from them as possible. Chop the meat and reserve.
Heat a large pot of water to a boil and salt it liberally. Cook the macaroni until just barely done according to directions on the box. Drain and reserve.
Finely chop the shallots and garlic. Sauté them in a little olive oil until they are soft. Remove from the oil and add to the lobster meat.
Grate the cheeses. Reserve ½ cup of the parmesan.
Place the remaining parmesan and the rest of the cheese and mascarpone in a double boiler. Stir them until the mixture starts to clump together. Slowly add the cream until the cheese is almost fully incorporated and the sauce is a good consistency. Taste and add salt if needed.
Toss the cheese mixture, macaroni and lobster meat together and spread in a buttered casserole dish. Cover and refrigerate overnight if needed.
Preheat the oven to 375 degrees.
Mix the breadcrumb and reserved parmesan over the mac and cheese and cook until the cheese is bubbly and the topping has browned. This will take about an hour if starting from cold; 10-15 if cooking right away.