1. Prepare the Fries

• If using fresh potatoes, scrub, peel (optional), and cut into ¼-inch thick fries.
• Soak cut fries in cold water for 30 minutes to remove excess starch (optional for crispier texture).
• Drain, pat dry, and toss with oil and a pinch of salt.
• Bake at 425°F (220°C) for 25–30 minutes, flipping halfway, or air fry at 400°F for 15–20 minutes until golden and crisp.
• Alternatively, fry in hot oil (350°F/175°C) for 5–6 minutes in batches.
• If using frozen fries, cook according to package instructions until crisp.

2. Caramelize the Onions

• In a skillet, heat butter or oil over medium-low heat.
• Add chopped onions and a pinch of salt. Cook slowly for 15–20 minutes, stirring frequently.
• Add small splashes of water as needed to deglaze and soften the onions.
• Onions should be golden brown, soft, and sweet by the end.

3. Make the Special Sauce

• In a small bowl, whisk together mayo, ketchup, mustard, relish, vinegar, sugar, and a pinch of salt and pepper.
• Taste and adjust seasoning as needed. Set aside or chill until serving.

4. Assemble the Animal Style Fries

• Transfer hot fries to a serving tray or platter.
• While still hot, immediately top with cheese slices so they melt.
• Spoon caramelized onions evenly over the cheese.
• Drizzle or dollop the special sauce generously across the top.
• Serve immediately with extra sauce on the side if desired.