Hot sandwiches with cheese and French onions

Ingredients:

• 1 tbsp unsalted butter, plus extra for spreading
• 1 tbsp. l. olive oil
• 2 yellow or red onions, sliced ​​0.5 cm thick.
• 1 tbsp. l. dry sherry
• 0.5 tsp chopped fresh thyme
• 4 slices white American cheese
• 8 slices of rustic white bread
• 4 slices yellow American cheese

Preparation:

1. In a heavy-bottomed saucepan, melt the butter and olive oil over medium-high heat. Add the onion, season with salt and pepper, and spread into an even layer. Cover the pan and reduce the heat to medium-low. Sauté the onion for 10-15 minutes.
2. Then remove the lid and continue cooking, stirring frequently, until the onions are caramelized, 25-30 minutes. Add the sherry and scrape up any browned bits from the bottom of the pan. Add the thyme and season with salt and pepper to taste.
3. Heat a skillet over medium-low heat. Place 1 slice of white American cheese on 4 slices of country bread and 1 slice of yellow American cheese on 4 more slices of bread. Spread the onions evenly on half the bread, then top with the remaining slices and butter both sides of the sandwiches.
4. Place the sandwiches in the skillet; cover with a metal bowl (be careful, it will become hot) and cook until crispy, about 2-3 minutes. Flip, cover again, and cook until the cheese is melted and the sandwiches are golden brown, another 2-3 minutes.