The Preparation
Preheat oven to 450°F.
Quarter onions and place in baking dish, drizzle with olive oil, add fresh thyme, salt and pepper.
Roast at 450°F for 20 minutes.
Mix cream and Dijon mustard, pour over onions, top with grated asiago cheese.
Bake for an additional 20 minutes.
Broil briefly to brown the cheese on top.