Ingredients:

  • 225 g (1 ¾ cups) All-purpose flour (plain flour)
  • 1 g (½ teaspoon) Fine sea salt (for pastry)
  • 115 g (8 tablespoons or ½ cup) Unsalted butter, cut into 1 cm cubes, kept very cold
  • 50–60 ml (3–4 tablespoons) Ice water
  • 4 large Red onions (about 900 g total), peeled and thinly sliced
  • 30 ml (2 tablespoons) Olive oil
  • 15 ml (1 tablespoon) Balsamic vinegar
  • 5 g (1 teaspoon) Granulated sugar
  • 2 g (½ teaspoon) Fine sea salt (for onions)
  • Black pepper to taste
  • 180 g (6 oz) Soft goat cheese (Chèvre log), divided
  • 120 ml (½ cup) Double cream (heavy cream), 35% fat
  • 2 large Eggs, room temperature
  • 5 g (1 teaspoon) Fresh thyme leaves
  • 1 g (¼ teaspoon) Fine sea salt (for filling)
  • Pinch of freshly grated nutmeg (optional)

Instructions:

  1. Make the Pastry: Combine flour and salt. Cut or rub in the very cold butter until the mixture resembles coarse breadcrumbs (either by hand or using short pulses in a food processor). Add ice water gradually until the dough just comes together. Do not overwork.
  2. Chill Dough: Form the dough into a flat disc, wrap tightly, and refrigerate for a minimum of 30 minutes.
  3. Caramelise Onions: Heat oil in a large pan over medium-low heat. Add the sliced onions and cook, stirring occasionally, for 30–40 minutes. The heat must be low to prevent scorching and encourage slow browning.
  4. Finish Onions: When the onions are dark golden-brown and sticky, stir in the sugar, balsamic vinegar, salt, and pepper. Cook for 2 more minutes until the liquid has evaporated. Set aside to cool completely.
  5. Roll and Line: On a lightly floured surface, roll the chilled dough to a thickness of about 3 mm (1/8 inch). Carefully line the 9-inch (23 cm) tart tin, pressing the dough into the fluted edges. Prick the base all over with a fork, cover, and freeze for 15 minutes.
  6. Blind Bake: Preheat oven to 190°C (375°F). Line the frozen pastry shell with parchment paper, fill with baking weights, and bake for 15 minutes. Remove the paper and weights and return the shell to the oven for an additional 8–10 minutes until the base is dry. Trim the excess pastry overhang. Reduce the oven temperature to 170°C (340°F).
  7. Prepare Custard Base: In a medium bowl, whisk together the cream, eggs, salt, thyme, and nutmeg until just combined.
  8. Incorporate Cheese: Stir in 120 g (4 oz) of the crumbled goat cheese into the custard mixture.
  9. Layer: Spread the cooled caramelised onions evenly across the bottom of the pre-baked pastry shell.
  10. Assemble: Carefully pour the cream/egg mixture over the onions. Arrange the remaining 60 g (2 oz) of goat cheese attractively on top.
  11. Final Bake: Bake for 25–30 minutes at 170°C (340°F), or until the custard is set, firming up around the edges but still having a very slight wobble in the centre. Allow the tart to cool in the tin for 10 minutes before carefully removing the outer ring and serving.