Spanish sweet potato tortilla

Ingredients:

• 1 onion, sliced ​​into thin half rings
• 2 sweet potatoes, peeled, halved lengthwise and cut into thin half-moon slices
• 6 tablespoons extra-virgin olive oil
• 8 large eggs
• 1 tbsp. grated manchego cheese (about 110 gr.)
• 2 tbsp sherry vinegar
• 1 teaspoon Dijon mustard
• 3 heads Belgian endive, halved lengthwise and cut into 2.5cm pieces.
• 3 tbsp finely chopped almonds
• 3 tbsp finely chopped chives

Preparation:

1. Preheat oven to 425°F (220°C). In a medium oven-safe nonstick skillet, combine the onion, sweet potato, 1/4 cup olive oil, 1/2 teaspoon salt, and a few grinds of black pepper. Cover and cook over medium heat, stirring occasionally, until the sweet potato is tender but not falling apart, 6-8 minutes.
2. In a large bowl, beat the eggs and season with salt. Place the sweet potatoes in the bowl with the eggs and stir. Add the cheese. Place the pan over medium heat, add the egg mixture, and spread the sweet potatoes with a spatula. Cook until the mixture begins to set around the edges, 1-2 minutes. Transfer the pan to the oven and bake until tender, 12-15 minutes.
3. Meanwhile, combine the vinegar and mustard in a large bowl; add the remaining 2 tablespoons olive oil. Add the endive, almonds, and 2 tablespoons chives; toss to combine, and season with salt and pepper to taste.
4. Transfer the tortilla to a cutting board, cut into wedges, and arrange among plates. Sprinkle with the remaining 1 tablespoon chives and serve with the endive salad.