Buttery, golden and beautifully savoury, this Black Garlic Mustard, Caramelised Onion & Gruyère Tart is an elegant addition to any entertaining table.
Sweet, slowly caramelised red onions are layered over our Noosa Black Garlic Mustard, topped with nutty Gruyère cheese and fragrant fresh thyme, then baked until the puff pastry is irresistibly crisp and golden.
The mustard brings a delicious depth of black garlic umami, perfectly balancing the sweetness of the onions and the richness of the melted cheese.
Simple enough for a weekend lunch yet sophisticated enough for entertaining, this French-inspired tart is guaranteed to impress.
Serves: 4–6
Prep Time: 15 minutes
Cook Time: 45–50 minutes
Ingredients
For the Caramelised Onions
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3 medium red onions, thinly sliced
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2 tbsp extra virgin olive oil
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1 tbsp unsalted butter
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1 tsp brown sugar
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1 tbsp balsamic vinegar
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¼ tsp sea salt
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Freshly ground black pepper
For the Tart
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1 sheet good-quality butter puff pastry, approximately 24–25 cm square, thawed
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3 tbsp Noosa Black Garlic Mustard
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120 g Gruyère cheese, freshly grated
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1 tbsp fresh thyme leaves
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1 egg, lightly beaten
To Serve
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Extra fresh thyme leaves
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Freshly ground black pepper
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A simple rocket salad, optional
Method
Step 1: Caramelise the Onions
Heat the extra virgin olive oil and butter in a large frying pan over medium-low heat.
Add the thinly sliced red onions and sea salt.
Cook gently for 20–25 minutes, stirring occasionally, until the onions become soft, sweet and deeply golden.
Avoid cooking over high heat, as the onions should caramelise slowly rather than brown too quickly.
Step 2: Finish the Caramelised Onions
Add the brown sugar and balsamic vinegar to the softened onions.
Continue cooking for another 2–3 minutes until the mixture becomes glossy and beautifully caramelised.
Season with freshly ground black pepper, remove from the heat and allow to cool slightly.
Step 3: Prepare the Puff Pastry
Preheat the oven to 200°C (180°C fan-forced).
Place the thawed puff pastry onto a sheet of baking paper.
Using a sharp knife, lightly score a 2 cm border around the edges, taking care not to cut all the way through the pastry.
Prick the centre of the pastry several times with a fork to prevent excessive rising.
Step 4: Add the Black Garlic Mustard
Spread the Noosa Black Garlic Mustard evenly across the centre of the pastry, keeping the scored border clear.
Sprinkle half the grated Gruyère cheese over the mustard.
Step 5: Layer the Caramelised Onions
Arrange the caramelised onions evenly over the cheese.
Scatter over the remaining Gruyère and fresh thyme leaves.
Brush the pastry border lightly with the beaten egg.
Step 6: Bake Until Golden
Transfer the tart, still on its baking paper, to a large baking tray.
Bake for approximately 20–25 minutes, until the pastry is beautifully puffed and golden and the Gruyère is melted and lightly bubbling.
Step 7: Finish and Serve
Remove the tart from the oven and allow to rest for approximately 5 minutes.
Scatter over extra fresh thyme leaves and freshly ground black pepper.
Slice into generous portions and serve warm with a simple rocket salad, or cut into smaller squares for entertaining.
Noosa Black Garlic Tip
For a little extra black garlic richness, replace the regular balsamic vinegar used to caramelise the onions with Noosa Black Garlic White Balsamic Vinegar.
The caramelised onions can be prepared up to two days ahead and stored in the refrigerator, making this tart particularly easy to assemble when entertaining.
For a delicious variation, add a few crumbles of creamy goat's cheese before baking.
Why We Love This Recipe
Our Noosa Black Garlic Mustard adds an unexpected layer of savoury complexity to this classic French-inspired flavour combination.
Its subtle acidity balances the sweet caramelised onions and rich, nutty Gruyère, while the black garlic brings a beautifully rounded umami depth.
Spread directly over buttery puff pastry, the mustard ensures every bite is packed with flavour.
Elegant, versatile and surprisingly simple, this is a wonderful recipe for sharing with friends and family.
Products Used:
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Noosa Black Garlic Mustard
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Noosa Black Garlic White Balsamic Vinegar, optional