01 -  Preheat oven to 475°F and place pizza stone inside if using. 
 02 -  Bring medium pot of salted water to a boil. Cook elbow macaroni until just al dente, 6 to 7 minutes. Drain and set aside. 
 03 -  In saucepan, melt butter over medium heat. Whisk in flour and cook for 1 minute. Slowly pour in milk, whisking constantly until mixture thickens and turns smooth, about 2 to 3 minutes. 
 04 -  Remove from heat and stir in cheddar cheese until melted. Season with salt and pepper. Add cooked macaroni, mixing thoroughly. Set aside. 
 05 -  In a bowl, toss shredded chicken with BBQ sauce until evenly coated. 
 06 -  On lightly floured surface, stretch or roll pizza dough into 12-inch round. Transfer to parchment-lined baking sheet or hot pizza stone. 
 07 -  Spread prepared mac and cheese evenly over pizza dough, leaving 1/2-inch border around edge. 
 08 -  Distribute BBQ chicken over mac and cheese. Sprinkle with mozzarella and top with red onion slices. 
 09 -  Bake for 12 to 15 minutes until crust is golden and cheese is bubbling and starting to brown. 
 10 -  Remove from oven. Drizzle with extra BBQ sauce and sprinkle with cilantro if desired. Slice and serve hot.