Prepare the Onions: Preheat your oven to 190°C (375°F). In a large skillet, heat 2 tablespoons of olive oil and 2 tablespoons of unsalted butter over medium heat. Once hot, add the thick onion rounds and sear them for about 3–4 minutes on each side until they develop a beautiful golden brown color. Remove the onion rounds from the skillet and place them in a single-layer baking dish.
Make the Creamy Sauce: In a separate saucepan, pour in 1 cup (250ml) of heavy cream and heat it gently over low heat. As it begins to warm, gradually stir in 1 cup (100g) of shredded Asiago cheese and ½ cup (50g) of grated Parmesan cheese. Continue to stir until the cheese melts and forms a smooth sauce. Add 1 teaspoon of garlic powder, ½ teaspoon of smoked paprika, and season with salt and black pepper to suit your taste.
Assemble and Bake: Pour the creamy sauce over the seared onion rounds in the baking dish. For an extra cheesy topping, sprinkle additional Asiago cheese on top of the sauce. Carefully place the baking dish in the preheated oven and bake for 25–30 minutes, or until the cheese is bubbly and turns a lovely golden brown.
Garnish and Serve: Once baked, remove the dish from the oven and allow it to cool for about 5 minutes. For a fresh touch, sprinkle with chopped fresh parsley before serving to add a pop of color and flavor.