Preheat oven to 375ºF. Grease a 13" x 9" baking pan.
Bring a pot of salted water to boil and cook pasta to al dente. Drain, rinse under cold water and return to pot.
Heat 2 Tbsp butter in a sauté pan over medium heat. Add shrimp and garlic and cook, stirring, 4-5 minutes until no longer pink. Season to taste. Add to pasta pot.
Heat the remaining butter in a saucepan over med-high heat. Whisk in flour and cook, stirring, for 1 minute. Slowly whisk in the milk, bring to boil while stirring. Reduce heat to low, add nutmeg and simmer for 2 minutes.
Add the cheeses in 3-4 additions, stirring well after each. Season to taste. NOTE: if you like your sauce thinner, add more milk to reach desired consistency.
Pour over pasta and stir well. Transfer to the baking dish and sprinkle with panko. Bake for 25 minutes. Enjoy!