Step 1

Add 1 1/2 Tbsp butter and olive oil to a skillet and heat over MED-LOW heat. Add diced onions, salt, pepper, fresh thyme and 1 tsp of fresh rosemary to the hot skillet and saute, stirring often, until onions are soft and starting to brown, about 10 minutes.

Step 2

Stir brown sugar into the onions and cook another minute.

Step 3

Transfer onions to a plate.

Step 4

Spread one side of two pieces of bread with a little bit of mayonnaise.

Step 5

To the same skillet, add remaining butter and rosemary, and heat over MED heat. Swirl to coat the bottom of the skillet with the melted butter.

Step 6

Add both pieces of bread, mayonnaise side down, and cook until bread is golden brown and crunchy, about 2-3 minutes.

Step 7

As soon as you add the bread to the skillet, add a bit of cheese to the top of each piece of bread. Once it starts to melt a little, sprinkle a couple tablespoons of the caramelized onions over the top of one of the pieces of bread.

Step 8

When the bread is good and golden brown, sandwich the pieces of bread together and cook on LOW until cheese is fully melted.

Step 9

Transfer to a plate, repeat with remaining slices of bread and ingredients.

Step 10

Slice and enjoy!