Moules Frites (Steamed Mussels And Fries) | Saveur

Ingredients

• 1 tsp. Dijon mustard
• 1 egg yolk
• 1 cup canola oil, plus more for frying
• 2 tsp. white wine vinegar
• 2 tsp. fresh lemon juice
• ¹⁄₂ tsp. kosher salt, plus more to taste
• Freshly ground black pepper, to taste
• 2 lb. Yukon Gold potatoes, peeled and cut into 1/4"-thick sticks
• 2 ¹⁄₂ lb. mussels, debearded and scrubbed
• ²⁄₃ cup dry white wine
• 2 tbsp. unsalted butter, cubed
• 3 ribs celery, finely chopped
• 1 ¹⁄₂ leeks, light green and white parts, cut into 1/4"-thick slices
• ¹⁄₂ large yellow onion, finely chopped