How to Make It
Process half of the cauliflower in a food processor until very finely chopped. Transfer to a medium saucepan. Repeat with the remaining cauliflower. Add stock and cornmeal to pan; bring to a boil over high. Cover and reduce heat to medium-low; simmer, whisking often, until cauliflower is cooked and mixture is thickened, about 10 minutes. Remove from heat. Stir in cheese, pepper, and salt. Cover to keep warm.
Combine tomato sauce, 3 tablespoons water, mustard, ketchup, garlic powder, chile powder, and onion powder in a small saucepan. Bring to a simmer over medium. Simmer, stirring often, until slightly thickened, about 6 minutes. Stir in shredded chicken. Divide cauliflower mixture among 4 bowls. Top evenly with chicken mixture. Sprinkle with scallions.