Preheat oven to 350 degrees and generously grease casserole dish with 1/2 tbsp. butter.
Bring large pot of salted water to a boil.
Add pasta to water when boiling and cook al dente about 5 minutes and drain well.
Rinse pasta with cold water and set aside.
Meanwhile on stove top over medium heat melt butter.
Add finely chopped garlic, ground mustard, and cornstarch to butter to form a roux.
Stir in half & half cream and allow to heat about 3-4 minutes till warm and starting to slightly thicken.
Turn off heat and add cheese reserving 1 cup of the cheese for topping.
Season with salt to taste.
Add cooked pasta to cheese sauce and stir till combined.
Pour into prepared casserole dish and bake in preheated oven 15 minutes.
Remove from oven and stir in chopped dill pickles and top with remaining cheese.
Lower temperature to 300 degrees.
Bake about 8-10 more minutes till cheese is bubbly.