Ingredients

• 907 g (2 lb) Yukon Gold potatoes (≈ 2½–3″ long each), scrubbed, ends trimmed so they have flat sides.
• 295 ml (1¼ cups) beef or chicken stock (unsalted preferred) :contentReference
• 60 ml (¼ cup) room-temperature water 
• 1 (28 g / 1 oz) packet dry onion soup & dip mix (e.g., Lipton Recipe Secrets) 
• 1 large onion (≈283 g / 10 oz), thinly sliced (≈1½ cups) 
• 6 medium cloves garlic, finely chopped 
• 60 ml (¼ cup) dry sherry :contentReference
• 1 tsp fresh thyme (chopped) or equivalent dried food-service thyme 
• 113 g (8 Tbsp / 4 oz) unsalted butter, divided 
• 57 g (½ cup) shredded Gruyère cheese 
• 57 g (½ cup) shredded low-moisture mozzarella cheese (or substitute Swiss/Fontina)
• ½ cup (≈28 g) panko breadcrumbs (optional for crust) 
• Fine sea salt & freshly ground black pepper, to taste
• Chopped fresh parsley or extra thyme sprigs, for garnish

Equipment

• Large heavy skillet or sauté pan (for browning potatoes)
• Oven-safe baking dish or the same skillet if oven-proof
• Colander, spoon, knife, mandoline or sharp knife for slicing potatoes

Method

1. Pre-heat & prepare. Preheat oven to 230 °C (≈ 450°F). Trim both ends of each potato so they sit flat, then halve cross-wise. Pat dry. Season both sides with ~1 tsp salt & ¾ tsp pepper. :contentReference[oaicite:13]{index=13}
2. Brown potatoes. In a large skillet, melt 2 Tbsp butter + ~1 Tbsp oil over medium-high. Add potatoes cut-side down and cook until golden and crusted (~5-7 minutes). Transfer browned potatoes to baking dish, crusted-side up.
3. Caramelise onions. In the same skillet, reduce heat to medium. Add remaining butter, sliced onions and a pinch of salt. Cook, stirring occasionally, ~25-30 minutes until jam-brown and soft. Add garlic in the last minute. Stir in sherry, scrape up bits, and cook ~2 minutes to reduce. Stir in thyme. 
4. Make onion-stock mix. In a measuring jug, whisk together the stock, water and onion soup mix. Pour this liquid around the potatoes in the baking dish (not over the cheese yet).
5. Top and bake. Spoon caramelised onions over the potato rounds. Sprinkle Gruyère + mozzarella evenly across the top. Optionally, scatter panko breadcrumbs for extra crunch. Bake uncovered for ~10-12 minutes until cheese melts and bubbles. Then optionally broil ~1-2 minutes for a golden crust. 
6. Finish & serve. Let dish rest ~5 minutes before serving. Garnish with chopped parsley or thyme. Serve warm as an indulgent side or pair with roast chicken / steak & crisp salad

Notes & Substitutions

• Potatoes: Yukon Golds give creamy interiors and crisp crusts; you may use Russets but texture will differ. 
• Vegetarian option: Use vegetable stock instead of meat stock; omit bacon if adding. (No bacon in this version, but you could add for variation.)
• Cheese swap: If you can’t get Gruyère, use Swiss, Fontina or a high-quality cheddar—ensure it melts well. 
• Make-ahead: You can caramelise onions ahead of time. Assemble the rest and refrigerate. Bring to room temperature, add a few minutes to bake time. 
• Crunchy top: Panko breadcrumbs add texture; omit if you prefer purely gooey. The original recipe emphasises a buttery sauce finish. 

Approx. Nutrition (per serving)

~400 kcal • ~22 g fat • ~12 g protein • ~40 g carbs
Estimated. Varies by cheese and stock used.

FAQ