Step 1. Add oil to a large pot of boiling salted water, add the pasta and cook al dente according to the directions on the package. Drain well.
Step 2. Heat the milk in a small saucepan, but don't allow it to boil.
Step 3. In a large pot, melt 6 tablespoons of the butter and add the flour. Cook over low heat for 2 minutes, stirring constantly with a whisk. Still whisking, add the hot milk and cook for 1 to 2 minutes, until thickened and smooth.
Step 4. Off the heat, add the Gruyere, Cheddar, 1 tablespoon salt, the pepper and nutmeg and stir until the cheese melts.
Step 5. Stir in the cooked pasta and lobster. Place the mixture into 6 to 8 (2-cup) gratin dishes.
Step 6. Melt the remaining 2 tablespoons of butter, combine with the bread crumbs and sprinkle on top. Bake for 30 to 35 minutes, until the sauce is bubbly and the pasta is browned on top.