Caramelized onions deglazed with beef broth turn this grilled cheese into a French onion soup sandwich.

Jessica Webster | AnnArbor.com

I've been obsessed with caramelized onions, and who wouldn't be? They're magic. You start with stinky, pungent onions, and suddenly — or rather, not so suddenly — you have these gorgeous, deeply-sweet caramel-brown onions that taste good on anything.

They are, of course, the most important ingredient in French onion soup, that relic of the Mad Men era, from a time when America was thoroughly obsessed with French cuisine. Though I love French onion soup with all of my heart, I rarely make it at home, mostly because it's a pain in the neck to scrape all that hardened cheese off the soup bowls when I'm cleaning up at the end of the night.

But what if there was another French onion soup delivery method? What if you reduced some beef broth into the caramelized onions, seasoned the whole deal with some thyme… and instead of topping the soup with bread and cheese, you put the whole thing between two slices of bread and some melted cheese?

Last year I shared a recipe with you for a delicious bouillabaisse sandwich. A French onion soup sandwich didn’t seem so far-fetched. And in fact, it’s so not far-fetched that you can already find a similar sandwich on the menu at the Cheese Dream cart in Mark's Carts. Great minds think alike, apparently. Or at least, cheese and caramelized onion-obsessed minds.

The key to this sandwich is to take your time. Allow a good 40 minutes to caramelize the onions. This may seem like a long time to spend making a grilled cheese sandwich, but don’t think of it that way. Think of it as a soup you can eat with your hands. That’s definitely worth the time.

French Onion Soup Sandwiches (loosely adapted from JoyTheBaker.com)

• 2 yellow onions
• 3 tablespoons butter
• 1 tablespoon olive oil
• 1/4 teaspoon fresh ground pepper
• 1/2 teaspoon kosher salt
• 1/2 teaspoon dried thyme or 1 teaspoon fresh thyme leaves
• 1/2 cup beef broth (or beer if you’re vegetarian)
• 4 slices good sandwich bread
• 1 tablespoon softened butter or margarine
• 2 ounces gruyere cheese, sliced for sandwiches

Step one: The onions

Peel the onions, slice them in 1/4-inch rounds, then slice the rounds in half.
Place a medium, heavy-bottomed saucepan over medium heat and heat the butter and olive oil. When the fats get hot and start to shimmer, stir the onions in.

Cook the onions over medium heat, stirring frequently. The onions will begin to sweat, and steam will rise from the pan. After about 5 minutes, add the salt, pepper and thyme, stir well, turn the heat to low and stir occasionally.

Now is the time when patience is required. You will want to turn the heat up. You will ache with the need to speed this process up. Do not. Just keep remembering that you want sweet, brown onions. You do not want bitter, burned onions.

Be patient. Grab a magazine. Turn on the radio. Invite your kid into the kitchen and talk about music. (Or teach him to caramelize onions!) Do not turn the heat up.

If the pan gets dry during this process, you can add some more butter or oil to keep the onions from sticking.

After about 15-20 minutes over low heat, brown bits will start to form. This is when you want to start deglazing the pan. Add the beef broth a tablespoon or so at a time. Scrape the bottom of the pan with your spatula and stir well.

Keep cooking over low heat, stirring occasionally, adding more beef broth as brown bits form, for another 10-15 minutes. Once the onions have reduced and are a beautiful caramel color, you’re good to go. If you’ve got leftover beef broth, add that now. And if you do that, you get to turn the heat up to medium for just a bit, until the beef broth evaporates and has been absorbed into the onions. Now turn off the heat and set those beauties aside.

Step two: The sandwich

At this point, you’re basically making a grilled cheese sandwich. Butter four slices of bread. Set the two slices on a cutting board with butter side down, then layer on cheese, then onions, then more cheese. Top with the final slices of bread, butter side up.

Heat a large frying pan over medium heat. Add the sandwiches (butter side down) and cover. Cook until the bread starts to brown, about 3 minutes. Carefully flip the sandwiches and cook for another minute or two, then remove from heat. Slice the sandwiches and serve immediately. Then wait for the other sandwich recipient to shower you with praise and thanks.

Jessica Webster leads the Food & Grocery section for AnnArbor.com. You can reach her at JessicaWebster@AnnArbor.com.