Old-Style Onion Tart

Ingredients

• 250 g All-purpose flour (Sift before use)
• 125 g Cold butter (Cut into small cubes, keep refrigerated until use)
• 1 pinch Fleur de sel (Adjust to taste)
• 75 ml Cold water (Add gradually until a dough ball forms)
• 1 teaspoon Herbes de Provence (Optional, to flavor the dough)
• 500 g Pink onions (Peeled and sliced into strips)
• 2 tablespoons Olive oil (For cooking the onions)
• 1 tablespoon Whole grain mustard (Whole seeds for texture)
• 200 ml Liquid cream (20% fat)
• 1 Egg (At room temperature)
• to taste Salt
• to taste Black pepper
• 50 g Grated cheese (optional) (Gruyère, Comté or Emmental)

Instructions

1. Prepare the dough

   In a large bowl, combine the flour, fleur de sel and Herbes de Provence (if using). Add the cold butter cubes and work with your fingertips until small visible butter specks form.

   Time: PT10M

2. Incorporate water and form the dough

   Gradually pour the cold water (about 75 ml) while mixing until a ball forms. If the dough seems too dry, add a little more water; otherwise shape a disc and do not add more water.

   Time: PT5M

3. Rest the dough

   Wrap the dough ball in plastic wrap and place it in the refrigerator for 20 minutes.

   Time: PT20M

4. Prepare the onions

   Peel the onions and cut them into thin strips.

   Time: PT5M

5. Sauté the onions

   Heat the olive oil in a skillet over medium heat, add the onions and sauté for 20 minutes, stirring regularly until they are soft and lightly caramelized.

   Time: PT20M

6. Let the onions cool

   Remove the pan from the heat and let the onions warm for a few minutes.

   Time: PT5M

7. Roll out the dough

   On a lightly floured surface, roll the dough into a disc about 3 mm thick and place it in a high-sided tart pan. Fold the edges and lightly prick the base.

   Time: PT5M

8. Apply the mustard

   Spread the whole grain mustard evenly over the dough base.

   Time: PT1M

9. Arrange the onions

   Distribute the caramelized onions evenly over the mustard.

   Time: PT2M

10. Prepare the cream mixture

    In a bowl, whisk the liquid cream with the egg, a pinch of fleur de sel and pepper. Mix lightly.

    Time: PT3M

11. Pour the mixture

    Gently pour the cream mixture over the onions, leaving a small border free.

    Time: PT1M

12. Add cheese (optional) and pepper

    Sprinkle the grated cheese on top and add a turn of black pepper.

    Time: PT1M

13. Bake

    Bake the tart in a preheated oven at 180°C for 40 minutes, until the crust is golden and the filling set.

    Time: PT40M

    Temperature: 180°C

14. Rest before serving

    Remove the tart from the oven and let it rest for 10 minutes before slicing.

    Time: PT10M

Nutrition Facts

Calories

350

Protein

8 g

Carbohydrates

30 g

Fat

22 g

Fiber

3 g