1: Prepare the Onions

• Preheat your oven to 450°F (230°C).
• Lightly grease a baking dish with olive oil or a nonstick spray.
• Arrange the onion slices in a single layer at the bottom of the dish. Ensure the slices are evenly spaced for consistent roasting.
• Drizzle olive oil generously over the onions and sprinkle with chopped thyme, salt, and freshly ground black pepper.

 2: Roast the Onions

• Place the baking dish in the preheated oven and roast for approximately 20 minutes.
• Check for caramelization; the onions should soften and turn slightly golden around the edges. This step enhances their natural sweetness, forming the base of the dish.

 3: Prepare the Creamy Asiago Sauce

• While the onions are roasting, pour 1 cup of heavy cream into a small saucepan.
• Heat the cream over medium heat, allowing it to simmer gently without boiling.
• Whisk in 2 teaspoons of Dijon mustard for a tangy, robust flavor.
• Gradually add ¼ cup of grated Asiago cheese, stirring continuously until it melts into a smooth, creamy sauce.
• Taste the sauce and adjust seasoning if necessary, adding a pinch of salt or pepper.

 4: Assemble the Dish

• Remove the roasted onions from the oven and evenly pour the creamy Asiago sauce over the top, ensuring every slice is coated.
• Sprinkle the remaining ¼ cup of Asiago cheese across the dish for a bubbly, cheesy topping.

 5: Bake to Perfection

• Cover the baking dish with foil and return it to the oven.
• Bake for an additional 20 minutes until the onions are tender, the cheese is melted, and the sauce is bubbling around the edges.
• Remove the foil during the last 5 minutes of baking for a golden, slightly crispy topping.

 6: Serve and Enjoy

• Allow the dish to cool slightly before serving to let the flavors meld.
• Garnish with extra thyme for added aroma and a touch of greenery.
• Serve warm alongside roasted meats, creamy pastas, or hearty salads for a cozy, satisfying side.