Harrison Ford’s Secret-Ingredient Grilled Cheese: The Science of Umami Balance and Cheese Melting

Warm the olive oil in a skillet over medium heat. Add the thinly sliced onions along with a pinch of sea salt. Sauté slowly, stirring regularly, until the onions soften, release their moisture, and turn a rich, golden-brown caramel color (about 15 to 20 minutes). Transfer the sweet onions to a small dish and set aside.

Lay the 4 sourdough bread slices flat on a clean cutting board. Spread 1 tablespoon of softened butter evenly over one side of each slice—this will be the outer crisping surface. Flip the slices over and spread a thin, even layer of Dijon mustard across the opposite interior faces.

Take 2 slices of bread and place them butter-side down into a cool skillet or griddle. Divide half of the shredded sharp cheddar and Gruyère evenly over the Dijon-coated tops. Layer the caramelized onions over the cheese, sprinkle with black pepper and fresh thyme leaves, then top with the remaining shredded cheeses to bind the sandwich top.

Place the remaining 2 bread slices on top, mustard-side facing inward and butter-side facing up. Turn the burner to medium-low heat. Grill gently for 3 to 4 minutes per side, pressing down softly with a spatula so the butter browns evenly while the cheeses melt completely. Once the sourdough is deep golden-brown and the cheese is oozing out the sides, remove from heat, rest f-l-koujina (in the kitchen) for 1 minute f-l-board (on the cutting board), slice diagonally, and serve warm f-l-gass3a (at the table).