Heat oven to 350 degrees. Cook macaroni in plenty of rapidly boiling
salted water until done, about 10 minutes. Drain well and set aside.
Melt butter (1 stick); saute chopped onion and minced garlic until
soft, about 5 minutes. Whisk in flour to make roux. Cook until mixture
is smooth, about 5 minutes. Whisk in milk and cream; simmer until
mixture is thick and creamy, about 15 minutes. Add garlic mixture,
mustard, grated Jack, 1 cup grated Cheddar, grated Parmesan and 1/2
cup crumbled blue cheese. Return to heat till melted.