Lightly coat the interior of a 6-quart Crock Pot with nonstick cooking spray, making sure to cover both the bottom and sides. Set aside.
In a large pot, bring salted water to a boil. Add the macaroni and cook for about 6 minutes to soften them, but do not fully cook. Drain the pasta using a colander. While the pasta cooks, start making the cheese sauce.
In a large nonstick skillet, melt the butter over medium heat. Once the butter is nearly melted, add the shredded cheddar cheese and whisk continuously until the cheese is fully melted and smooth. Remove from the heat and pour the mixture into the prepared Crock Pot.
Add the condensed cheddar cheese soup, milk, sour cream, salt, pepper, and dry mustard to the Crock Pot. Whisk thoroughly. If using, incorporate the beaten eggs at this stage. The melted cheese will appear lumpy; continue whisking to combine as best as possible.
Add the partially cooked macaroni to the Crock Pot, stirring well to ensure all the noodles are coated with the cheese mixture.
Cook on LOW for 2 to 2 1/2 hours, stirring twice throughout the cooking time. The dish is ready when the macaroni has absorbed all the liquid.