You say “French onion soup,” and I start the flashback sequence: I’m 9 years old, sitting in a restaurant 18 shades of brown, burning my tongue on cheese stretching so much you’d think it was multiplying. It’s a brute force attack of pleasure: salty beef broth and the fatty chew of broiled cheese. There’s a crouton drowning in there somewhere, but really, it’s just a life raft for more cheese.
But when I was in culinary school, I learned to make French onion soup the “serious” way: You sweat onions slowly for hours, developing their vegetal sweetness, before simmering them with some mild beef stock and flashing under the broiler with just a few wisps of cheese. The subtle complexity of onions becomes the star. It’s got all the elements of kid food, but calibrated for grown-ups.
I was thinking about this soup the other day, the play of flavors and textures, and more importantly how it’s made from barely anything at all, as I was getting ready to cook out of my half-empty fridge. There were a couple leeks, a small hunk of cheese, and it occurred to me that maybe someone should keep that crouton out of the soup entirely and build everything on top of it instead.
I melted the leeks, I broiled some cheese on bread, I scrambled a pair of eggs (they looked lonely, and it was brunchtime), and what happened was a kind of time-warp magic. It was crisp and tender, plush and chewy, and full of the soft, round flavor of onion and cheese. Everything the kid and the cook in me’s ever loved about French onion soup, without scalding my tongue.
French Onion Soup Sandwich
Makes 2 sandwiches
2 medium-to-large leeks (You can use onions, but it’ll take longer, and the flavor will be a little sweeter and less delicate)
2 tablespoons butter, divided
Beef bouillon mix or mushroom powder, to taste
4 slices of levain, sourdough, or other hearty bread
1 ounce Parmesan, Piave Vecchio, or other hard cheese (These cheeses broil to a firm chewiness; you can also use softer ones like Gruyere, etc.)
Salt and black pepper, to taste
1. Clean the leeks well: Cut them where the white parts turn dark green, and save the dark parts for another use. Slice the leeks in half lengthwise, and rinse them under running water, flipping through the leaves like a deck of cards to make sure all the dirt in between layers gets washed out. Don’t worry about getting them dry; the clinging water will help them steam. Slice the leeks into 1/8”half-moons.
2. Melt 1 tablespoon plus 1 teaspoon butter over medium heat in a smallish, heavy sauté or sauce pan. When the foaming stops, add the leeks, stir, and turn heat down to medium-low. Stir. Hang out. Crack the eggs into a cup, and beat together with a pinch of salt and pepper. Now you start to wait, and think fondly about all the friends you haven’t talked to in a while. Resolve to call them soon. When you get to wondering how your exes are doing, grate the hunk of cheese.
3. Stir the leeks every few minutes, making sure they’re not getting brown, adding a splash of water if they’re taking on some real color. What you want is the leeks to sweat until they look like they’re melting – leeks have a lot of pectin that gives them a gorgeous, jammy texture if you cook them long enough without browning the bejeezus out of them. (It’s hard to say when this will happen; it depends on the leeks, the pan, etc. I’d start with a guess of 12 minutes and go from there.)
4. Season the leeks to taste with black pepper and beef bouillon mix. “What? This is a local, organic, processed food-free kitchen!” you say. Ok, fine. Use dehydrated mushroom powder. If you don’t use either of these things, you can just go with salt and pepper, but you’ll be missing out on that fantastic umami meatiness of the French onion soup of my childhood.
5. When the leeks are nearly done, cover 2 slices of bread with the cheese, and broil all 4 until the cheese is molten and the bread toasted. Spread the leeks between the two slices of toast.
6. Heat a small nonstick sauté pan over medium heat and melt the remaining 2 teaspoons butter. Pour in the eggs and stir; cook just until they’re set but still moist and turn them out onto the leeks. Top each egg with the cheese-covered bread and serve.
Note: If you really want to get down egg-wise, you can also use Ruth Reichl’s method for creamy, slow-scrambled eggs.
Another note: If you'd like, you can serve the sandwich knife-and-fork style. Add a little more cheese to the top slice of bread, and broil it until it gets a little brown in spots. Top the sandwich with the cheese facing up, press down lightly to squish together the egg, leeks, and bread inside, and serve.
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