Cook pasta until al dente according to package directions. Drain, rinse with cold water, and drain again.
Place butter in a saucepot over medium-low heat. Melt butter and add garlic and onion; cook 5 minutes or until onion is softened.
Whisk in flour; cook 1 minute. Pour in milk; bring mixture to a boil over medium-high heat, whisking frequently.
Reduce heat to medium-low, and simmer 3 minutes or until sauce is smooth and thickened. Remove from heat, and whisk in the two cheeses, and the mustard, chives, and cayenne. Stir in half the salt and pepper.
Fold in pasta and lobster. Pour into a greased baking dish.
Combine crushed crackers and the melted butter for the crackers. Stir in remaining salt and pepper. Sprinkle over casserole.
Bake for 30 minutes or until crust is crisp and sauce bubbles. Let stand 5 minutes before serving.
Price Per Serving
based on average national price: excludes store savings and local grocery store pricing