Preheat oven to 350 degrees F.

Lightly grease a 9x13 baking dish with butter or with non-stick cooking spray. Set aside.

Cook pasta according to the box directions, aiming for al dente. Drain, mix with olive oil, and set aside.

Place a large saucepan over medium heat, and once it's hot, add the butter. Stir and melt the butter, being careful not to burn it.

Add the flour and whisk until thoroughly combined with the melted butter.

While still whisking, gradually add the milk, stirring to combine. Take your time, and don't rush through this step.

In a small bowl, whisk cream and cornstarch until fully combined and the cornstarch is fully dissolved. Add the mixture to the pan and stir to combine.

Add the evaporated milk and stir to combine. Add onion powder, garlic powder, ground thyme, paprika, mustard, red pepper flakes, and salt.

Stir over medium heat, bring the mixture to a boil, and let it simmer for about 2 minutes.

Stir in sour cream and cream cheese until thoroughly combined. If the sauce is too thick, add more milk or some chicken broth. Taste and adjust for salt and pepper.

Reduce heat to low and add 3 cups of cheddar cheese and 1 cup of freshly grated or pre-shredded mozzarella cheese. Stir to combine until the cheese is fully melted.

Remove the pan from heat and add the cooked elbows macaroni. Stir to combine.

Transfer the mixture to the prepared casserole dish.

In a medium bowl combine cracker crumbs with melted butter and stir using a fork until fully combined.

Level the top with a spatula and sprinkle 1 cup of mozzarella cheese and 1 cup of cheddar cheese evenly over the surface of the casserole.

Sprinkle the Buttery Cracker Topping evenly over the surface and top with chopped cooked bacon, if using.

Bake the casserole uncovered in the preheated oven for 25-30 minutes until the top is golden brown and bubbly.

Remove from oven and let it rest for 15 minutes before serving.

Serve topped with extra bacon and, if desired, chopped parsley.