Ingredients
Scale
- 1 sheet puff pastry (thawed)
- 3 large yellow onions (thinly sliced)
- 2 tbsp butter
- 1 tbsp olive oil
- 1 tsp sugar
- Salt (to taste)
- 1 tsp fresh thyme leaves
- 1 cup shredded Gruyère cheese
- ¼ cup heavy cream
- 1 egg (for filling)
- Black pepper (to taste)
Instructions
- In a skillet, melt butter with olive oil over medium heat. Add onions, sugar, and salt; cook for 25–30 minutes until golden brown. Stir in thyme and set aside.
- Preheat the oven to 400°F (200°C).
- On a parchment-lined baking sheet, place the puff pastry. Score a border around the edges and prick the center with a fork.
- Brush the edges with beaten egg and bake for about 10 minutes until lightly golden.
- In a bowl, whisk together cream, egg, pepper, and Gruyère. Spread Dijon mustard on the pastry base (if using), pour in the cheese mixture, and top with caramelized onions.
- Bake for an additional 15–18 minutes until puffed and golden brown.
- Prep Time: 15 minutes
- Cook Time: 45 minutes
- Category: Appetizer/Main
- Method: Baking
- Cuisine: French
Nutrition
- Serving Size: 1 slice (85g)
- Calories: 220
- Sugar: 4g
- Sodium: 350mg
- Fat: 14g
- Saturated Fat: 7g
- Unsaturated Fat: 6g
- Trans Fat: 0g
- Carbohydrates: 20g
- Fiber: 2g
- Protein: 5g
- Cholesterol: 45mg