Preheat oven to 375°. In large skillet, cook chorizo over medium-high heat 7 minutes or until cooked through, stirring occasionally. With slotted spoon, transfer to paper towel-lined plate.
In large saucepot, cook macaroni as label directs; drain and return to saucepot.
In large skillet, melt butter over medium-high heat. Whisk in garlic and flour and cook 2 minutes or until lightly browned. Whisk in half and half, salt, nutmeg and pepper, and cook 4 minutes or until smooth and slightly thickened. Stir in cheeses, and cook 2 minutes or until smooth, stirring frequently. Remove from heat and whisk in cream. Fold chorizo and cheese mixture into macaroni until combined; transfer to 2-quart baking dish.
In small bowl, combine breadcrumbs, olive oil and cilantro; evenly sprinkle over macaroni mixture. Bake 30 minutes or until edges bubble and top is browned.