Heat oven to 375°F; grease 2-quart dish. Cook macaroni in large pot with tablespoon salt to 1 minute short of package time; drain.
Meanwhile, melt sauce butter in saucepan. Cook jalapenos over medium 4 minutes; add garlic 30 seconds.
Add milk and cream cheese; stir over low until smooth. Remove from heat; add Monterey Jack, sauce salt, and pepper.
Fold in macaroni; transfer to dish. Toss panko with topping butter; scatter thinly over pasta.
Bake 20 to 25 minutes until bubbling and golden. Rest 5 minutes.