Start by cooking the macaroni until it’s al dente. While the macaroni is cooking, preheat your oven to 350 degrees.
The next step is to make a roux. To do this, simply melt 2 tablespoons of butter in a saucepan over medium heat. Stir in enough flour to make the roux, about 2-2.5 tablespoons. After the flour and butter are well combined, slowly stir in the entire can of evaporated milk. Let the milk mixture heat up a bit, then slowly add 2.5-3 cups of the shredded sharp white cheddar cheese, and about 3/4 of the blue cheese, stirring continuously so that it doesn’t stick to the bottom of the saucepan. Continue cooking until all of the cheese is melted.
Drain the water out of the macaroni and dump it into an 8×8 casserole dish. Then, pour your melted cheese mixture over the macaroni, and stir it all together, making sure that every piece of macaroni gets covered with the cheese mixture.
Next, sprinkle the crushed Saltine crackers evenly over the macaroni.
Then, sprinkle the remaining shredded sharp cheddar cheese and blue cheese over the Saltine crackers.
Top the macaroni with a few small pieces of butter.
Cover the macaroni with aluminum foil and cook at 350 degrees for about 25 minutes.
Remove the aluminum foil, and cook for another 10-15 minutes, until the cheese is melted and the Saltine crackers have turned golden brown.
