Preheat your oven to 350. Lightly spray a 3 qt baking dish or au gratin pan with cooking spray and set aside.
Grate/shred cheeses and set aside.
Cook the pasta according to the package instructions, minus 1 minute. Drain.
While the pasta is cooking, start the roux by melting 6 tbsp of butter in a saucepan or dutch oven over medium heat.
Once the butter is melted, whisk in the flour into the butter; whisk until the mixture is bubbly and golden, about 1 minute.
To the butter and flour mixture, gradually whisk in the heavy cream and milk. Continue whisking until you see bubbles; continue to cook and whisk for 2 minutes.
Add half the cheese and whisk until smooth and melted. Then, add the second half of the cheese and whisk until smooth and melted.
Add salt & pepper, to taste.
Add in cooked pasta, stirring until combined.
Add in chopped shrimp; stir until combined.
Pour mixture into baking dish, set aside.
In a medium pan, melt remaining 6 tbsp of butter over medium heat. Once melted, add panko and bread crumbs until well coated in butter.
Top your pasta with the panko-bread crumb mixture.
Bake about 25-30 minutes until bubbly and the panko crumbs are golden brown. If they start to brown too quickly, top the baking dish with a piece of foil to prevent burning.