Step 1

Heat the olive oil over medium heat in a large pan or cast iron skillet. When it's hot, add the sliced onions. Cook and stir often with a wooden spoon until the onions start to soften, about 20 minutes.

Step 2

Add the butter and cook for another 20 minutes, continuing to stir every 2-4 minutes. Keep a close eye on your onions that they don't burn. Reduce heat if necessary.

Step 3

Add the salt, sugar, cinnamon, and ground black pepper and continue cooking for another 15 minutes (this is when they'll really start to brown). Once you reach the 12 minute mark, add the chopped garlic.

Step 4

Pour in the red wine to deglaze the pan. Using your wooden spoon, scrape the bottom and sides of the pan to get at any caramelized bits. Let cook for 2-3 minutes, or until the wine has mostly cooked off.Set the onions aside.

Step 5

Melt butter 4 tbsp. of butter a microwave-safe dish with a pinch each of rosemary and thyme (both or either). Brush the melted butter onto one side of each slide of bread.

Step 6

Place two slices butter-side-down into the pan or cast iron skillet. Top both slices with the caramelized onions.

Step 7

Add the shredded or sliced white cheddar on top of the onions.

Step 8

Close the sandwiches using the other slices of bread, butter side up. Place the skillet on medium heat, and cook for about 5-minutes, or until the bottom is golden and toasty.While the sandwiches cook, turn your oven to broil.

Step 9

Once the bottom half of the bread is toasted in the pan, it's time to move your cast-iron skillet to the oven.****Let the sandwiches broil for a minute or two until the top piece of bread is golden and toasty.*****

Step 10

Remove the skillet or sheet from the oven, and sprinkle the gruyere on top of the sandwiches.Return sandwiches to oven, and let cook for another minute or two, or until the cheese is golden and bubbly.

Step 11

Remove from the oven and cut in half. Sprinkle with more rosemary and thyme and serve hot.