Set a large pot over medium-high heat and add the butter.

Once butter is melted, add the garlic. Saute just until fragrant, about 30 seconds. Sprinkle the flour into the pot and whisk until a thick paste forms. Continue whisking until the flour is very lightly golden, 30 seconds to 1 minute. Slowly pour half the milk into the pot, whisking to dissolve the flour. When no lumps remain, pour in the remaining milk while continuing to whisk.

Cook the sauce, whisking constantly, until it begins to bubble and thicken. Once sauce is thickened, turn off the heat. Stir in the Parmesan cheese, salt, and black pepper. Add the corn kernels and stir until thoroughly coated in sauce.

Pour the corn mixture into the prepared baking dish.

Place the cracker crumbs and shredded cheese in a mixing bowl and add the melted butter. Mix with a fork until the crumbs are evenly moistened.

Sprinkle the crumbs in an even layer over the corn mixture.

Bake the casserole on middle rack of oven until topping is deeply golden and dish bubbles at edges, 35-40 minutes.

Check to see that casserole is done. Remove from oven or add time as needed.

Allow the casserole to rest for 10-15 minutes before serving.