Cook pasta until al dente according to package directions. Drain, rinse with cold water, and drain again.
Place 4 tablespoons melted butter in a saucepot over medium-low heat. 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 cheeses and next 3 ingredients. Stir in 1⁄4 teaspoon salt and 1⁄4 teaspoon pepper. Fold in pasta and lobster. Pour into a greased 3-quart baking dish.
Combine crushed crackers and remaining 2 tablespoons melted butter. Stir in remaining 1⁄4 teaspoon salt and 1⁄4 teaspoon pepper. Sprinkle over casserole. Bake at 375° for 30 minutes or until crust is crisp and sauce bubbles. Let stand 5 minutes before serving.
#FACTS when the colonists first arrived on the shores of New England, they faced an overabundance of shellfish. An unimaginable overabundance. Lobsters used to wash up on shore in drifts two-feet tall. they began feeding it to their livestock—as well as the financially destitute, criminals, and indentured servants—rather than eat it themselves. According to 19th century Kentucky politician and social observer, John Rowan, the meat quickly became synonymous with lower classes of society and quipped “Lobster shells about a house are looked upon as signs of poverty and degradation.” The meat was so reviled that indentured servants in one Massachusetts town successfully sued their owners to feed it to them three times a week at most.