Prepare macaroni and cheese according to package directions.

Gradually stir in beaten eggs into the cooked macaroni and cheese.

Grease a 12-inch pizza pan.

Spread the macaroni and cheese mixture evenly onto the prepared pizza pan to form the crust.

Bake at 375°F (190°C) for 10 minutes, or until the crust is set.

While the crust is baking, cook ground beef and chopped onion in a large skillet over medium heat until the beef is no longer pink.

Drain off any excess grease from the beef mixture.

Stir pizza sauce into the cooked beef and onion mixture.

Spread the meat mixture evenly over the baked macaroni and cheese crust.

Sprinkle the drained mushrooms, pepperoni slices, and shredded Mexican cheese blend evenly over the meat mixture.

Bake for an additional 10-15 minutes, or until a thermometer inserted in the crust reads 160°F (71°C) and the cheese is melted and bubbly.