Wo-grown Up Grilled Cheese Sandwich Recipe

Cook onions

Heat a medium skillet over medium heat. Add 1 tablespoon butter (or 1 tablespoon olive oil + 1 teaspoon butter) and let it melt and coat the pan.

Add the thinly sliced onion and 1/4 teaspoon salt. Stir to coat. Cook, stirring every 1–2 minutes, for 8–10 minutes until soft and translucent.

Reduce heat to medium-low. Continue to cook, stirring frequently and scraping browned bits from the pan, for another 15–20 minutes until the onions are deep golden brown. If the pan gets too dry or begins to burn, add 1–2 tablespoons water to deglaze.

If desired for extra sweetness and color, stir in 1/2 teaspoon brown sugar during the last 5 minutes of cooking. Remove from heat and let cool slightly. Reserve 1/2 cup for sandwiches and store any extra refrigerated for up to 3 days.

Grate/shred cheeses: combine 1.5 cups sharp cheddar and 3/4 cup Gruyère in a bowl. If using a third cheese (fontina/provolone), fold the slices into the mix.

Mix spreads: in a small bowl mix 2 teaspoons mayonnaise and 1 teaspoon Dijon mustard. Spread the butter on the outside faces of all 4 bread slices (about 1/2 tablespoon per slice). On the inside face of two slices, spread the mayo-mustard mixture evenly.

Layer sandwiches: On the two bread slices with mayo-mustard, divide the shredded cheese evenly (about half the cheese mixture per sandwich). Top each with 1/4 cup caramelized onions, two slices of optional bacon or ham if using, and a sprinkle of freshly ground black pepper and 1/8 teaspoon garlic powder each (if using). Close sandwiches with the remaining buttered bread slices, buttered side out.

Preheat skillet and cook: heat a large nonstick or cast-iron skillet over medium-low to medium heat. Place one sandwich in the dry skillet, reduce heat if needed to avoid burning. Cook for 3–4 minutes until the bottom is golden brown and cheese begins to melt.

Flip and finish: carefully flip the sandwich and press gently with a spatula. Cook another 3–4 minutes until the second side is golden and cheese is fully melted. If bread is browning before cheese melts, lower heat and cover the skillet with a lid or tent with foil for 1–2 minutes to trap heat and finish melting the cheese.

Repeat with second sandwich. Transfer sandwiches to a cutting board and rest 1 minute, then slice in half on the diagonal.

Serve: plate sandwiches with optional pickles or a small salad. Leftover caramelized onions keep the flavor rich; store sandwiches wrapped in foil if taking to go and reheat in a 350°F (175°C) oven for 8–10 minutes to refresh.