Quick Recipe Version (TL;DR)
Quick Ingredients
- 1.5 lb (680 g) 80/20 ground beef
- 2 large yellow onions, thinly sliced
- 6 slices Swiss cheese, halved (12 pieces)
- 24 cocktail rye slices (about 2-inch squares)
- 5 tbsp unsalted butter, divided
- 1 tbsp neutral oil
- 1 1/4 tsp kosher salt; 3/4 tsp black pepper
- Thousand Island: 1/2 cup mayo, 3 tbsp ketchup, 2 tbsp sweet pickle relish, 2 tsp white vinegar, 1/4 tsp paprika, pinch salt
Do This
- 1. Stir together Thousand Island; chill.
- 2. Caramelize sliced onions in 2 tbsp butter + 1 tbsp oil over medium-low 35–40 minutes.
- 3. Portion beef into twelve 2 oz (56 g) balls; keep cold.
- 4. Butter-toast 24 rye squares in 3 tbsp butter until golden; keep warm.
- 5. Heat griddle/skillet to 425°F (very hot). Smash 6 balls, season, cook 1–1 1/2 minutes; flip, top with onions + Swiss, cover 30–45 seconds to melt. Repeat.
- 6. Swipe bottom rye with Thousand Island, add patty, cap with rye; serve hot.
Why You’ll Love This Recipe
- Deeply caramelized onions bring sweet, savory richness without extra fuss.
- Smash-style patties mean lacy, crispy edges and juicy centers in minutes.
- Butter-toasted rye and melty Swiss deliver classic patty melt vibes—mini-sized.
- A quick, tangy Thousand Island ties everything together and doubles as a dip.
Grocery List
- Produce: 2 large yellow onions
- Dairy: Swiss cheese slices, unsalted butter, mayonnaise
- Pantry: 80/20 ground beef, cocktail rye bread, ketchup, sweet pickle relish, white vinegar, paprika, kosher salt, black pepper, neutral oil (canola/avocado), optional dill pickle chips for serving
Full Ingredients
Caramelized Onions
- 2 large yellow onions (about 1 1/2 lb / 680 g), halved and thinly sliced
- 2 tbsp (28 g) unsalted butter
- 1 tbsp (15 ml) neutral oil
- 1/2 tsp kosher salt
- 1/2 tsp sugar (optional, jump-starts browning)
- 2–3 tbsp water, as needed for deglazing
Thousand Island Sauce
- 1/2 cup (120 g) mayonnaise
- 3 tbsp (45 g) ketchup
- 2 tbsp (30 g) sweet pickle relish
- 2 tsp (10 ml) distilled white vinegar
- 1/4 tsp paprika (sweet or smoked)
- Pinch kosher salt
Beef Patties
- 1.5 lb (680 g) 80/20 ground beef, cold
- 1 1/4 tsp kosher salt
- 3/4 tsp freshly ground black pepper
- 1 tbsp (15 ml) neutral oil (for the skillet/griddle)
Bread & Cheese
- 24 cocktail rye slices (about 2-inch squares) or rye sandwich bread cut into 24 squares
- 3 tbsp (42 g) unsalted butter (for toasting bread)
- 6 slices Swiss cheese, halved (12 pieces)
Step-by-Step Instructions
Step 1: Mix the Thousand Island
In a small bowl, whisk together the mayonnaise, ketchup, relish, vinegar, paprika, and a pinch of salt until smooth and pink. Cover and refrigerate for at least 15 minutes (up to 1 week) so the flavors meld.
Step 2: Caramelize the onions low and slow
In a large skillet over medium heat, melt 2 tbsp butter with 1 tbsp oil. Add the onions, 1/2 tsp salt, and optional sugar. Cook, stirring every 3–4 minutes, until the onions soften and turn translucent, about 10 minutes. Reduce heat to medium-low and continue cooking 25–30 minutes more, stirring occasionally and adding 1–2 tbsp water as needed to deglaze any browned bits. Onions are done when deep golden-brown and jammy. Keep warm over low or rewarm before assembly.
Step 3: Portion and prep the beef
Divide the ground beef into 12 equal portions (2 oz / 56 g each). Roll lightly into loose balls without compressing. Place each on a small square of parchment (for easy smashing). Keep chilled until cooking. Mix the salt and pepper in a small dish so you can season quickly at the stove.
Step 4: Butter-toast the rye
In a separate large skillet over medium heat, melt 3 tbsp butter. Add the rye slices in a single layer and toast until golden-brown, 2–3 minutes per side. Work in batches if needed. Transfer to a warm plate or 200°F (95°C) oven to keep hot and crisp.
Step 5: Smash, sear, and melt the cheese
Heat a cast-iron skillet or griddle over medium-high until very hot, about 425°F surface temperature if using an infrared thermometer (a drop of water should sizzle on contact). Lightly film with 1 tbsp oil.
Working in two batches of 6, place the beef balls (parchment-side up) on the hot surface. Remove parchment and immediately smash each into a thin patty, about 3 inches wide and 1/4 inch thick, pressing firmly for 10 seconds with a stiff spatula or burger press. Season each patty with a pinch of the salt-pepper mix. Cook until edges are deeply browned and lacy, 60–90 seconds. Scrape and flip. Top each with about 1 tbsp caramelized onions and a half-slice of Swiss. Cover with a lid or invert a metal bowl to trap heat and melt the cheese, 30–45 seconds more. Patties should reach 160°F for well-done; they cook very fast because they’re thin. Transfer to a warm plate and repeat with remaining patties.
Step 6: Build the sliders and serve
Swipe the bottom of each toasted rye square with 1–2 tsp Thousand Island. Set a cheesy patty on top, then cap with another rye square. Press gently, secure with picks if desired, and serve immediately while the cheese is melty and the bread is crisp. Optional: offer extra sauce and dill pickle chips on the side.
Pro Tips
- For ultra-lacy edges, smash immediately when the beef hits the hot surface and do not move until ready to flip.
- Keep the patties thin; thickness over 1/4 inch reduces crisp edges and slows cooking.
- Deglaze onions with a splash of water (or 1 tsp Worcestershire) near the end to intensify flavor.
- Use parchment squares under the beef balls to keep your spatula clean and prevent sticking.
- Diamond Crystal and Morton kosher salts differ in saltiness; if using Morton, start with about 3/4 of the listed salt and adjust.
Variations
- Mushroom-Swiss Patty Melt Sliders: Sauté 8 oz sliced cremini mushrooms in butter; fold into the onions for extra umami.
- Spicy Kick: Add 1–2 tsp hot sauce to the Thousand Island and a few pickled jalapeño slices per slider.
- Turkey or Veg: Use 93/7 ground turkey (cook to 165°F) or a firm veggie patty, smashed gently and seared until crisp.
Storage & Make-Ahead
Caramelized onions: cool and refrigerate up to 4 days; rewarm with a splash of water. Sauce: refrigerate up to 1 week. Toast bread just before serving for best texture. Portion beef balls up to 24 hours ahead; keep covered and cold. Cooked patties keep 3 days refrigerated; reheat in a covered skillet over medium-low 2–3 minutes per side until hot. Assembled sliders are best fresh and do not freeze well, but cooked patties and onions freeze up to 2 months.
Nutrition (per serving)
Approximate per slider: 330 calories; 20 g fat; 19 g carbs; 17 g protein; 2 g fiber; 630 mg sodium. Values will vary with bread brand, cheese thickness, and sauce amount.
