Caramelized Onion and Blue Cheese Tart Recipe

<ul class="ingredients-main-list"><li class="ingredients-single-item">For the pastry:</li><li class="ingredients-single-item">200g plain flour</li><li class="ingredients-single-item">100g cold unsalted butter, cubed</li><li class="ingredients-single-item">1/4 teaspoon salt</li><li class="ingredients-single-item">3-4 tablespoons ice-cold water</li><li class="ingredients-single-item">For the filling:</li><li class="ingredients-single-item">4 large onions (approximately 750g), thinly sliced</li><li class="ingredients-single-item">30g unsalted butter</li><li class="ingredients-single-item">2 tablespoons olive oil</li><li class="ingredients-single-item">2 teaspoons fresh thyme leaves (or 1 teaspoon dried)</li><li class="ingredients-single-item">1 tablespoon brown sugar</li><li class="ingredients-single-item">2 tablespoons balsamic vinegar</li><li class="ingredients-single-item">150g blue cheese, crumbled (Roquefort, Gorgonzola or Stilton)</li><li class="ingredients-single-item">3 large eggs</li><li class="ingredients-single-item">200ml double cream</li><li class="ingredients-single-item">50ml whole milk</li><li class="ingredients-single-item">1/2 teaspoon salt</li><li class="ingredients-single-item">1/4 teaspoon freshly ground black pepper</li><li class="ingredients-single-item">Pinch of freshly grated nutmeg</li></ul>

<ul class="equipment-main-list"><li class="equipment-single-item">23cm (9-inch) loose-bottomed tart tin</li><li class="equipment-single-item">Baking beans or dried rice (for blind baking)</li><li class="equipment-single-item">Baking parchment</li><li class="equipment-single-item">Rolling pin</li><li class="equipment-single-item">Large heavy-based frying pan</li></ul>

<ol class="no-list-style"><li class="MethodStepper"><h4 class="step-title">Step 1</h4>Start by making the pastry. In a large bowl, combine the flour and salt, then add the cold butter. Using your fingertips, rub the butter into the flour until the mixture resembles breadcrumbs (keeping ingredients cool helps develop a flaky texture). Gradually add ice-cold water, one tablespoon at a time, mixing with a knife until the dough just comes together. The secret to flaky pastry is minimizing handling and keeping everything cold.</li><li class="MethodStepper"><h4 class="step-title">Step 2</h4>Form the dough into a disc, wrap in cling film and refrigerate for at least 30 minutes. This resting period allows the gluten to relax, preventing shrinkage during baking and ensuring a tender crust.</li><li class="MethodStepper"><h4 class="step-title">Step 3</h4>While the pastry chills, prepare the caramelized onions. Heat the butter and olive oil in a large heavy-based frying pan over medium-low heat. Add the sliced onions with a pinch of salt and cook very slowly, stirring occasionally, for about 30-35 minutes. Patience is key here—proper caramelization cannot be rushed, as the slow cooking develops complex sweet flavors as the onions' natural sugars break down.</li><li class="MethodStepper"><h4 class="step-title">Step 4</h4>When the onions have turned a deep golden color, add the thyme, brown sugar, and balsamic vinegar. Continue cooking for another 5-10 minutes until the mixture is jammy and richly caramelized. Remove from heat and allow to cool completely.</li><li class="MethodStepper"><h4 class="step-title">Step 5</h4>Preheat your oven to 190°C (170°C fan/Gas 5). On a lightly floured surface, roll out the pastry to about 3-4mm thickness, making it large enough to line your tart tin with some overhang. Carefully transfer to the tin, pressing into the corners without stretching the dough. Trim the excess, leaving a small overhang to account for shrinkage.</li><li class="MethodStepper"><h4 class="step-title">Step 6</h4>Line the pastry case with baking parchment and fill with baking beans or dried rice. Blind bake for 15 minutes, then remove the beans and parchment and bake for another 5-7 minutes until the base is dry and lightly golden. This pre-baking ensures your crust won't become soggy from the filling.</li><li class="MethodStepper"><h4 class="step-title">Step 7</h4>Reduce the oven temperature to 180°C (160°C fan/Gas 4). Spread the cooled caramelized onions evenly over the base of the pastry case. Scatter about two-thirds of the crumbled blue cheese on top of the onions.</li><li class="MethodStepper"><h4 class="step-title">Step 8</h4>In a jug, whisk together the eggs, double cream, milk, salt, pepper, and nutmeg until well combined. Carefully pour this custard mixture over the onions and cheese, making sure not to overflow the tart case. Sprinkle the remaining blue cheese on top.</li><li class="MethodStepper"><h4 class="step-title">Step 9</h4>Bake the tart for 25-30 minutes until the filling is set but still has a slight wobble in the center (it will continue to firm up as it cools). The top should be golden and puffed. If the crust begins to darken too quickly, cover the edges with foil to prevent burning.</li><li class="MethodStepper"><h4 class="step-title">Step 10</h4>Remove from the oven and allow to cool in the tin for at least 15 minutes before carefully removing. This resting period allows the custard to fully set and flavors to meld. Serve warm or at room temperature, garnished with a few fresh thyme leaves if desired. The tart pairs beautifully with a simple green salad dressed with a light vinaigrette to balance the richness.</li></ol>