Preheat the oven to 325 degrees Fahrenheit.
Bring water to a boil in a large pot, adding elbow pasta and cooking for 1 minute less than directed on the packaging. Drain the pasta and drizzle with olive oil to prevent sticking.
While waiting for the water to boil/the pasta to cook, grate all of the cheeses. Toss together to mix and then separate into 3 bowls.
Melt ½ cup of butter in the saucepan over medium heat.
Add the flour and whisk to combine, cooking for about 1 minute.
Slowly pour in the milk and heavy whipping cream, whisking constantly.
Continue to whisk over medium until the mixture becomes thick.
Remove from heat and add one of the bowls of cheese mix, whisking to combine.
Mix the dry mustard, salt, ground black pepper, and cayenne pepper into the cheese sauce.
In a large bowl, combine the drained elbow pasta with the cheese sauce, stirring to combine.
Pour half of the pasta in a greased 9x13 baking dish. Top with the second bowl of mixed cheeses. Pour the remaining pasta on top of cheese and top with the final bowl of cheeses.
Melt 3 tablespoons of butter and mix with the crushed Ritz crackers.
Top with the Ritz cracker mixture and bake for 15-20 minutes, until the cheeses are bubbling. Garnish with parsley and/or bacon, if desired. Enjoy!