Savory Roast Beef Panini
E
By Emma
Certified Culinary Professional
•
Recipe tested & approved
Roast beef paninis served with a rich au jus dipping sauce. Uses sautéed onions cooked with butter and a hint of brown sugar for sweetness. The au jus made with beef broth, Worcestershire, and a powdered mix simmers down to a glossy, deeply flavored liquid. Roast beef slices warmed gently in the au jus to keep moisture. Layered with Havarti cheese and caramelized onions on softened, buttered bread toasted in a panini press. Fast cook, simple ingredients, full of texture contrasts and bold flavors. 4 servings, roughly 375 calories each. Protein-packed sandwich with a modest carb and fat profile.
Prep:
20 min
Cook:
10 min
Total:
30 min
Servings:
4 servings
#American
#sandwich
#panini
#roast beef
#caramelized onions
#au jus
#Havarti cheese
Caramelized onions in a skillet whisper golden sweetness, butter softens their edges like a gentle sigh. Roast beef sliced thin, soaking briefly in bubbling au jus—a deep, glossy river of beef broth and Worcestershire tang. Bread slathered with butter on both sides, toasted to crunch, melting cheese nestled inside with the savory onion and beef layers. You end up with a panini that crunches at the edges and melts in the center, dripping with rich jus you can’t help but dip into. I’ve played with timing, used leftover steak before, and always keep an eye on browning—too fast, and it burns; too slow, and it’s just soggy. That dance of heat makes or breaks it.
Ingredients
- 2 large yellow onions sliced thinly
- 1 ½ tbsp unsalted butter
- 1 tbsp light brown sugar
- ⅓ tsp salt
- ⅓ tsp freshly ground black pepper
- 2 cups low-sodium beef broth
- 2 tbsp Worcestershire sauce
- 1 packet au jus mix (around 0.75 oz)
- 10 oz deli-sliced roast beef (substitute leftover prime rib or steak strips)
- 8 slices sturdy sandwich bread (French or Italian works)
- 8 slices Havarti cheese (swap for Swiss or provolone)
- Butter for spreading generously
About the ingredients
Onions best sliced thin but not paper-thin; they need substance to caramelize properly. Butter amount flexible; less butter slows caramelization but cuts richness. Brown sugar brings out hidden sweetness—too much, and it burns quick. Beef broth low sodium for control on saltiness. Au jus packet adds bulk flavor but is replaceable with homemade beef stock plus extra Worcestershire and soy sauce if you have them. Roast beef slices vary widely; thicker cuts taste meatier but need longer warming. Havarti is creamy and melts nicely, but Swiss or provolone work too. Bread should be sturdy—stale bread’s toastiness helps resist too much moisture. Butter slices evenly to get that crisp exterior without burning.
Method
- Start by heating a large skillet over medium heat. Toss in the sliced onions, butter, brown sugar, salt and pepper. Listen for that gentle sizzle—not too fast, you want onions softening and turning golden but not burnt. Stir often, 6-7 minutes. When edges caramelize lightly, smell sweet and deep, scoop out two-thirds, save for topping later.
- Keep remaining onions in skillet. Pour in beef broth, Worcestershire sauce, and au jus mix powder. Whisk briskly to prevent lumps. Turn heat up to medium-high. The mix will steam and bubble. Watch for small rolling boil, then drop to low. Let it simmer, watching thickness. Should coat the back of a spoon in 5-6 minutes, glossy and reduced. Stir every so often to keep it even.
- Scoop ⅓ to ½ cup from this rich au jus into small serving bowls—aim for 5 total bowls. This is your dipping sauce, so plan well. Don’t skip because watery sandwiches are sad sandwiches.
- Back to the skillet—medium-low now—add your sliced roast beef. No stirring wild. Gently fold meat in the au jus. The beef warms through in about 5-7 minutes. Pink disappears, edges relax, juices absorb flavor. Stay patient; heat it right or risk dry tough beef.
- Fire up your panini press. Preheat fully. No procrastinating here means you avoid cold bread awkwardness.
- Butter one side of each bread slice liberally. Place butter side down on your work surface. On one slice, stack 2-3 slices of cheese depending on size, then dole out 1-2 tablespoons of the caramelized onions you saved. Spread evenly but not so thick it smushes cheese out.
- Drain excess liquid off warmed beef before laying a quarter of it over onions. Trust me—too wet and you get a soggy mess. Top beef with 2 more slices of cheese. Sandwich with second slice of bread, butter side facing up for that golden crust.
- Set sandwich in the panini press. Close gently and grill for about 3-4 minutes. Look for toasted, golden crust and melted gooey cheese peeking out. Adjust timing based on your press—listen for the pressing sounds and feel the sandwich firmness.
- Remove carefully. Let sit a minute to rest (if you can wait). Serve hot with the au jus dipping bowls. Thicker au jus means better dunking, so if too thin, quick simmer to concentrate.
- Tip: If using stale bread, toast slices lightly before assembling to resist sogginess. If your onions start browning too fast, lower heat and add a tablespoon of water to help them sweat instead.
- Alternative: Swap Worcestershire for a splash of balsamic vinegar for tangier au jus. Or toss some fresh thyme or rosemary in with your onions if feeling fancy.
Cooking tips
Caramelizing onions is key—watch for smell and color changes over exact time. Pull most out early to save for layering, but keep some as flavor base for au jus. Mixing liquids requires steady whisk to avoid lumps from powder mixes—heat carefully to thicker stage but don’t let reduce to dryness. Serve au jus warm not scalding to preserve subtle savory notes. Meat warming slow and gentle brings out juicy texture. When assembling, drain liquid off beef well—excess ruins bread texture. Panini press timing varies; listen to pressing clicks and peek when safe. Rest sandwich briefly to let melted cheese settle before cutting. Experiment adding fresh herbs in au jus or swapping onions with shallots or leeks for personal signature.
Chef's notes
- 💡 Onions slice too thin and they vanish into mush; aim for firm thin slices that brown over 6-7 minutes. Stir often but gently to avoid scorching. Brown sugar helps sweeten but flip heat low if edges burn quick. Pull most onions early for layering, keep some in skillet for au jus base. Watch aroma change from sharp to buttery sweet—it’s your signal.
- 💡 Whisk liquids fast or powder mix clumps. Bring to small rolling boil before drop to low simmer. Keep stirring every few minutes to stop drying or lumping. Thickness should coat spoon back shiny in 5-6 minutes—not thick gravy but not watery either. If too thin, quick longer simmer but guard against dryness.
- 💡 Warming beef in au jus needs patience. Medium-low heat with occasional gentle fold to keep texture. Pink fades gradually, edges relax, juices soak flavor without drying. Do not rush or stir aggressively, or beef fibers tighten and get chewy. Drain excess au jus off beef before assembling; too wet = soggy bread nightmare.
- 💡 Butter bread evenly but generously; uneven butter spots create hot spots that burn faster. Place slices butter side down on surface—gets better crust. Cheese layering matters: 2-3 slices depending on slice size helps melt evenly. Onion layer must be thin enough not to compress cheese out but enough for sweetness hit.
- 💡 Panini press preheat fully is key—cold press equals soggy mess. Close gently, listen for clicks if available to gauge pressure. Grill 3-4 minutes but adjust based on press power; peek carefully by lifting edge if unsure. Rest sandwich outside press for 1 minute minimum before cutting to set melted cheese and avoid filling spillout.
Common questions
Can I use shallots instead of onions?
Yes, shallots work but caramelize faster. Watch heat closely or sugar burns quickly. Flavor more subtle but sweet too. Try mix for complexity. Leeks possible but milder, may need longer cook time to soften properly.
What if my panini press isn’t hot enough?
Use skillet with weight instead. Butter bread, assemble sandwich then grill slow on medium heat. Flip carefully mid-way. Cheese melts differently. Press weight important for crust. Another fast workaround but expect slightly different texture.
My au jus is too thin how fix?
Simmer longer but watch closely. Stir to prevent burning. Or add slurry (cornstarch + water) in small amounts and stir briskly. If too thick, thin with beef broth bit by bit. Avoid salty adjustments late; low sodium broth upfront helps regulate.
How store leftovers?
Wrap sandwich tightly to avoid drying but don’t refrigerate too long (1-2 days max). Bread gets chewy but reheating in panini press or toaster oven restores some crunch. Au jus keep covered in fridge up to 3 days; reheat gently avoiding boil to keep flavor intact.
