Roast Beef and Caramelized Onion Panini

Roast Beef and Caramelized Onion Panini

A sandwich doesn’t need to be complex to be delicious, but it does need quality ingredients to come out well. In most cases, it also helps if the sandwich is toasted, as well. I always have a method of toasting a sandwich at home, so once I hit the store to look for filling ingredients, the sandwiches seem to make themselves.

This sandwich was completely inspired by one I saw a while back on This Daddy Cooks, where caramelized onions are used in place of uncooked in the filling. I love the melty sweetness of caramelized onions and couldn’t resist giving the whole concoction a try. I used roast beef (from Whole Foods, but leftovers will work equally well), havarti cheese and sweet panoche onions. I also used a whole-grain mustard, chock full of mustard seeds for lots of flavor and a little bit of texture, in addition to a little bit of mayo on the bread. I caramelized the onions in advance, as they can be stored in the fridge if you don’t have time to work on them right before assembling the sandwich.

I chose some simple panini rolls at the bakery for these sandwiches and used a technique I saw once on the Food Network for making panini, where the rolls are sliced in two and turned inside out. The filling is placed on what was once the outside of the sandwich and grilled. This way, you can use good, crusty bread without the crust getting so toasted that you can’t bite into it; the soft interior of the bread toasts up perfectly and the crust gets soft because it is exposed to melting cheese. I don’t butter the outsides of my bread before toasting it, as I’m not a fan of a greasy sandwich, but feel free to do so if you like.

This guide for the recipe, which is loose, makes two really large sandwiches. Serve with chips and have someone to share with.

Roast Beef and Caramelized Onion Panini
2 medium sweet onions, thinly sliced
1/2 lb sliced roast beef
1/4 lb havarti cheese (I didn’t quite use all the cheese)
whole grain mustard
2 large panini sandwich rolls

Cook the thinly sliced onions in a saucepan over medium heat, stirring occasionally, until they are golden and very tender, about 30 minutes. Turn off the heat.
Preheat your panini maker/sandwich press/waffle iron (yes, it works!).
Slice each of the panini rolls almost in half horizontally and turn inside out. Spread the crust side with mayonnaise and mustard, to taste, then add in about 1/4 lb of roast beef and half of the cheese into each sandwich.
Place sandwich on grill and toast until the new crust (what was once the inside of the bread), is golden and the cheese is melted.
Serve immediately.

Serves 2.


  1. Great sandwich, Nic. I also recommend the Boars Head roast beef – it’s terrific. Great trick on turning the rolls inside out.

  2. Looks wonderful. I was on a bit of a panini kick last week and had so much fun! :) I will have to add this on the make-soon list.

  3. Mmm looks yummy. My favourite sandwich is super simple. Either ham or a sausage between a slice of bread, with tar tar sauce as a spread. Slurp.

  4. Hay,

    Dang, that sounds tasty good. Wonder what it’d be like with pickles and/or horseyradish.


  5. What a fantastic technique, turning the bread inside out! I don’t know how I missed that episode on the Food Network, given that I watch 20+ hours a week :-) I’d been having difficulty making panini with rounder breads, like baguettes – this tip may have re-opened some panini possibilities!!

  6. OMG that is so yummy and I made this last week it was fab – off to check out some of your other recipes ….

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