Preheat the oven to 375 degrees F. Bring a large pot of water to a boil.
the butter in a cast-iron skillet set over low heatit is very important that this step be on low heat! Add the cubed cheddar and melt until creamy, stirring constantly. Stir in the egg
, taking care not to let it scramble.
While the cheese is melting, add the olive oil and salt to the pot of boiling water. Add the pasta; cook for 10 minutes. Strain
and return the pasta
to the pot.
Add the melted cheese and egg mixture to the cooked pasta, along with the cream of mushroom
soup, the evaporated milk
and the sour cream; stir, then add half of the cracker crumbs. Mix together until the pasta is well coated and the sauce
Add half of the pasta mixture to a 9-by-13-inch baking dish
and top with half of the shredded cheddar. Add the remaining half of the pasta, followed by the remaining shredded cheddar. Sprinkle the remaining cracker crumbs over the top. Bake for 40 minutes.