Cheesy Potato Recipe: Ultimate Gratin with Crispy Onions

Ingredients

• 2 lbs (900g) Yukon Gold or Russet potatoes, peeled
• 2 tbsp (30 ml) olive oil
• 1 tsp salt
• 1/2 tsp black pepper
• 1 large yellow onion, thinly sliced
• 1/2 cup (60g) all-purpose flour
• 1/4 tsp salt
• 1/4 tsp black pepper
• Vegetable oil, for frying (approx. 2 cups / 475 ml)
• 3 tbsp (45g) unsalted butter
• 3 tbsp (25g) all-purpose flour
• 3 cups (710 ml) whole milk
• 1/2 tsp salt
• 1/4 tsp nutmeg (freshly grated)
• 1 cup (115g) shredded Gruyere cheese
• 1 cup (115g) shredded sharp cheddar cheese