French Onion Grilled Cheese Sandwich

Ingredients

• 2 largeonions (yellow, sweet or red)
• 70 g (5 tablespoons), dividedbutter
• 15 ml (1 tablespoon)canola oil
• 5 ml (1 teaspoon)kosher salt
• 2 sprigsfresh thyme
• 45 ml (3 tablespoons)water or wine (white or red)
• 5 ml (1 teaspoon), optionalbouillon soup base
• 8 slicessourdough bread
• 113 g (4 ounces; about 1 cup grated)Gruyère cheese, grated

Instructions

1. 1

   Cook the onions

   Peel and slice the onions into large slices. In a large frying pan over medium heat, melt 14 g (1 tablespoon) of the butter with the canola oil. Add the onions and salt, turn the heat to low and cover the pan. Add the thyme sprigs. Stir about every 15 minutes, raising the heat if the onions are taking too long, while watching closely to prevent burning. Add the water or wine and the optional bouillon, stir them through, and cook until the onions become jammy and have cooked down. Remove the pan from the heat.

2. 2

   Build the sandwiches

   Spread 7 g (½ tablespoon) of butter on one side of each slice of bread, then place the slices buttered-side together. Layer cheese, caramelised onions and more cheese between the slices. Top each sandwich with another slice of bread, buttered side facing out, and repeat with the remaining bread.

3. 3

   Toast the first side

   Place the sandwiches buttered-side down in a frying pan over medium heat. Cover and cook for 3–4 minutes, or until the bread is golden.

4. 4

   Flip and finish

   Reduce the heat to medium-low and turn the sandwiches over. Cook for 2–3 minutes, until the bread is golden and toasted and the cheese has melted. The second side cooks faster, so keep an eye on it.

5. 5

   Serve hot

   Cut the sandwiches in half and enjoy while hot.

What is a French onion grilled cheese?

It is an American-style grilled cheese sandwich filled with the deeply savoury, sweet onions associated with French onion soup. French onion soup is a French dish built around cooked onions and broth; this sandwich borrows that flavour combination and pairs it with melted cheese.

Here, thyme-seasoned onions and Gruyère go between tangy sourdough slices. The combination works because the onions bring sweetness, the cheese adds savoury richness, and the bread can toast to a crisp exterior.

Nutrition and macros by portion

The nutrition label shows one serving as written: 565 calories, 17g protein, 60g carbs, 27g fat.

Most of the carbohydrates come from the sourdough, while butter and canola oil provide much of the fat. Gruyère contributes protein as well as fat, with smaller amounts of protein from the bread. To balance the plate, serve a sandwich portion with a generous side of salad or vegetables.

Choose and cook the onions

Onions: Yellow, sweet or red onions are all options in this recipe, so use whichever you prefer. Slicing them into large pieces gives them a substantial texture in the filling.

Low heat: Cover the pan and cook the onions gently, stirring about every 15 minutes. If they seem to be taking too long, raise the heat cautiously and watch for any signs of burning.

Build flavour in the pan

Thyme: Add the sprigs while the onions cook so their flavour infuses the mixture. Remove the pan from the heat once the onions have cooked down and become jammy.

Liquid and bouillon: Water or wine loosens the mixture, while the optional soup base adds savoury depth. Stir them into the onions and let them cook together until jammy.

Layer for a good melt

Cheese: Put Gruyère both beneath and on top of the onions. This gives the filling cheese on either side of the onion layer as it melts.

Butter: Spread butter on the outside of the bread, keeping the filling between the unbuttered sides. That outer coating helps the bread toast as the sandwich cooks.

Watch the toast and melt

First side: Cook the sandwiches covered over medium heat for 3–4 minutes, until the bread is golden. The lid is part of the method while the first side cooks.

Second side: Turn the sandwiches and lower the heat to medium-low for 2–3 minutes. Look for golden toast and melted cheese, and check the bread as the second side cooks faster.

Serve it with

Cut the sandwiches in half and serve them hot, while the Gruyère is still melted. A simple green salad or crunchy raw vegetables can add a fresh contrast to the rich, toasted filling.

For a soup-and-sandwich meal, serve alongside a light vegetable soup. Keep accompaniments simple so the onion and cheese flavours remain the focus.

Recipe notes & tips

• Stir the onions about every 15 minutes as they cook.
• Raise the heat only if the onions seem to be taking too long, and watch carefully for burning.
• Keep the cheese on both sides of the onion layer when assembling the sandwiches.
• Cover the pan while the first side cooks for 3–4 minutes.
• Watch the second side closely because it cooks faster than the first.
• Serve the sandwiches hot for the best melted-cheese texture.

Variations

• Use red onions: Swap them in for the yellow or sweet onions.
• Choose another wine: Use white or red wine in place of water, as suggested in the recipe.
• Skip the bouillon: Leave out the optional soup base for a simpler onion flavour.
• Add extra thyme: Increase the thyme sprigs for a more pronounced herbal note.
• Change the bread: Use another sturdy sliced bread that can hold the filling while toasting.

Common mistakes to avoid

• Cooking onions too fast: Keep the heat low and raise it cautiously if they are taking too long.
• Letting onions burn: Stir about every 15 minutes and watch closely, especially if increasing the heat.
• Leaving out the top cheese layer: Add cheese above the onions as well as beneath them.
• Toasting too long: Check the first side at 3 minutes and cook only until golden.
• Ignoring the second side: Check it early, as it cooks faster than the first.

How to store

Refrigerate leftover cooked sandwiches in an airtight container and eat within 2 days. Reheat in a frying pan over low heat until warmed through and crisp again; the bread may soften somewhat in storage.

Frequently asked questions