Wo-grown Up Grilled Cheese Sandwich Recipe

Cook onions slowly

Heat 1 tsp olive oil and 1 tbsp butter in a medium skillet over medium-low heat. Add the thinly sliced onions and 1/4 tsp kosher salt. Stir to coat and spread into an even layer. Cook gently, stirring every 3–5 minutes, until soft and deep golden, about 25–30 minutes.

Finish and season

When onions are richly browned, stir in 1 tsp brown sugar and 1 tsp balsamic vinegar. Cook 1–2 more minutes to deglaze and concentrate flavors. Remove from heat and set aside until ready to assemble sandwiches.

Prepare bread and butter

Spread a thin layer of softened butter evenly on one side of each slice of sourdough. These buttered sides will be the exterior for grilling. Reserve 1 tbsp butter for the pan if needed.

Mix internal spread

In a small bowl, combine the softened cream cheese, Dijon mustard, and a pinch (about 1/8 tsp) of black pepper. Mix until smooth and spreadable.

Assemble sandwiches

Place four slices of bread butter-side down on a work surface. On each slice, spread about 1 tbs of the cream cheese mixture evenly. Divide the grated cheddar and Gruyère evenly among the four slices (about 3/4 cup cheese mix per sandwich). Top cheese with about 1/4 cup caramelized onions, a few tomato slices (about 2–3 slices per sandwich), and a small handful of baby spinach (about 1/4 cup). Sprinkle each with a light pinch of kosher salt (about 1/8 tsp) and a few grinds of black pepper. Finish with the remaining bread slices, butter-side up.

Grill the sandwiches

Heat a large skillet or griddle over medium-low to medium heat. Add 1 tbsp butter or a little olive oil to the pan and swirl to coat. Place assembled sandwiches in the skillet (working in batches if needed). Press gently with a spatula or a weighted press. Cook for 3–4 minutes on the first side until golden brown and the cheese begins to melt. Flip carefully and cook another 3–4 minutes, pressing occasionally, until the second side is golden and the cheese is fully melted (internal temp ~140°F/60°C if using a thermometer). If bread is browning too quickly before cheese melts, lower the heat and cover the pan for 1–2 minutes to trap heat.

Rest and slice

Transfer finished sandwiches to a cutting board and let rest 1 minute to allow the cheese to set slightly. Slice each sandwich in half diagonally and serve immediately.

Serving suggestion

Serve with a small side salad or tomato soup. Optional: sprinkle chopped fresh chives or a light drizzle of olive oil on the cut surfaces for extra flavor.