Brie and Caramelized Onion Panini

Steps

1. 1

   Caramelize the onions

   • Peel and slice the 4 yellow onions into thin half-moons, about 1/8 inch (3 mm) thick.
   • Heat the butter in a large 12-inch (30 cm) skillet over medium heat.
   • Once melted and foaming, add all the sliced onions and 1/2 tsp salt.
   • Stir well to coat the onions.
   • Cook, stirring occasionally every 5–10 minutes, for 45–50 minutes, until the onions are very soft and deeply caramelized to a rich golden brown color.
   • They will seem wet at first but will gradually dry out and reduce in volume significantly—from about 4 cups of raw onions to roughly 1 cup of caramelized onions.
   • Around the 40-minute mark, when they are a deep golden color, strip the leaves from 2–3 thyme sprigs, stir them in, and cook for 2 more minutes.
   • Taste and adjust seasoning with black pepper and a pinch more salt if needed—they should taste slightly salty and deeply sweet.
   • This step can be done 1–2 days ahead; let cool completely and store in an airtight container in the refrigerator.

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   Ready when: Deep golden brown, very soft, reduced to about 1 cup total, rich caramel aroma

   Tip: Stir more frequently in the last 15 minutes to prevent sticking and burning. If browning too fast, lower heat to medium-low. Don't rush this step; slow caramelization develops the best flavor.

2. 2

   Slice the ciabatta bread

   • While the onions cook (around the 20-minute mark), using a long serrated bread knife, carefully slice each of the 2 ciabatta loaves in half horizontally to create 4 flat sandwich bases.
   • If the loaves are very long and difficult to handle, you can cut them lengthwise first to create quarters, then slice horizontally as needed.
   • You want each sandwich base to be about 4–5 inches (10–13 cm) long with two flat, exposed crumb sides.
   • Set the prepared bread aside.

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   Ready when: Clean horizontal cuts with light, airy crumb visible on cut surfaces

   Tip: Use a sharp serrated knife and a gentle sawing motion to prevent squashing the bread. A bread knife works best.

3. 3

   Slice the brie cheese

   • Remove the brie from the refrigerator and let it sit at room temperature while the onions finish cooking.
   • Once at room temperature (about 10 minutes total), place the brie on a clean cutting board.
   • Using a sharp, thin-bladed knife (or cheese knife), slice the brie into thin slices about 1/4 inch (6 mm) thick.
   • If the cheese is very soft and tears rather than slices cleanly, you can tear it into rough pieces instead—this is just as delicious.
   • Keep the brie slices ready on the cutting board.

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   Ready when: Brie sliced into thin, even pieces or naturally torn into rough chunks

   Tip: If brie is cold and hard to slice, let it sit at room temperature for a few more minutes. A thin knife dipped in hot water and dried can also help create clean slices.

4. 4

   Assemble the sandwiches

   • Remove the caramelized onions from heat and let cool for 2–3 minutes if very hot.
   • Lay out all 4 bottom pieces of ciabatta, cut-side up, on your work surface.
   • Divide the caramelized onions evenly among the 4 bottoms, spreading them in a single, even layer—roughly 1/4 cup (60 ml) of onions per sandwich.
   • Layer the brie slices (or pieces) evenly over the onions on each sandwich, covering them fully.
   • Cover each with the top piece of ciabatta, cut-side down, and press gently so the sandwich holds together but not so hard that you crush the bread.
   • All 4 sandwiches should now be assembled and ready to grill.

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   Ready when: Sandwiches stacked with brie and onions layered evenly, held together gently

   Tip: Keep onion and brie layers even so they grill consistently. Don't overstuff the sandwich or it will be difficult to grill.

5. 5

   Grill until golden and meltedOven 400°F / 205°C

   • Preheat your panini press (or a large grill pan) to medium-high heat (about 400°F / 200°C).
   • If using oil, lightly brush the exterior of each sandwich with the olive oil—just a thin coating on both the top and bottom.
   • If your press is non-stick, you may skip the oil.
   • Working in batches of 2 sandwiches at a time (most presses fit 2 comfortably), place sandwiches on the grill with even spacing.
   • Close the lid (or top grill plate) gently and cook for 3–4 minutes until the bread is deep golden brown and crispy and you see cheese beginning to ooze from the edges.
   • Do not press down hard on the lid; let the gentle heat do the work.
   • Transfer the grilled paninis to a clean cutting board and repeat with the remaining 2 sandwiches.

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   Ready when: Golden-brown exterior with slight char, cheese oozing from edges, warm throughout

   Tip: If bread is browning too fast but cheese isn't melting, lower heat to medium. Each press varies, so use the first batch as your test. The bread should be crispy and slightly charred, not pale.

6. 6

   Rest and serve

   • Transfer the paninis to a clean cutting board and let rest for 1 minute so the cheese sets slightly and the interior cools just enough to eat comfortably.
   • You can cut them diagonally for a more elegant presentation and to see the beautiful layers inside.
   • Serve immediately while hot, with a simple green salad dressed with lemon vinaigrette, arugula salad, or a cup of tomato soup on the side if desired.

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   Ready when: Cheese warm and slightly set, bread cooling to edible temperature

   Tip: These are best eaten immediately while the cheese is still gooey. If you must make ahead, see storage notes for reheating instructions.