Make the Pizza Dough: In a large bowl, combine warm water and sugar. Sprinkle the yeast over the top and let sit for 5-10 minutes until foamy. Add flour and salt to the yeast mixture. Mix with a spoon or your hands until a shaggy dough forms. Add olive oil, and knead for 5-7 minutes on a floured surface until smooth. Place dough in a greased bowl, cover with plastic wrap, and let rise in a warm place for 1-1.5 hours.

Cook the Macaroni: Cook the macaroni according to package directions until al dente. Drain and set aside.

Make the Cheese Sauce: In a large saucepan, melt butter over medium heat. Whisk in flour for 1-2 minutes, then gradually add milk, whisking until smooth. Bring to a simmer, reduce heat to low, and simmer for 5-7 minutes until thickened. Stir in salt, pepper, nutmeg, and cheese (3 cups cheddar, and Gruyere if using). Add cooked macaroni and stir until well coated.

Prepare the Pizza: Preheat your oven to 450°F (232°C) and place a pizza stone in the oven to heat. Punch down the risen dough and roll it out into a 12-14 inch circle. Transfer the dough to a baking sheet or pizza stone.

Assemble the Pizza: Spread the macaroni and cheese evenly on the dough, leaving a small border. Sprinkle remaining 1 cup cheddar cheese and Parmesan over the top. Add breadcrumbs if using.

Bake: Bake for 12-15 minutes until the crust is golden and the cheese is bubbly. Remove from the oven, cool slightly, slice, and garnish with fresh parsley if desired.