Sweet Potato & Caramelised Onion Tart with Brie, Thyme & Walnut Honey Crumble

Sweet Potato & Caramelised Onion Tart with Brie, Thyme & Walnut Honey Crumble is a gorgeous sweet-and-savoury tart made with flaky puff pastry, tender roasted sweet potatoes, deeply caramelised onions, and creamy Brie. Finished with a crunchy walnut honey crumble, fresh thyme, and an optional balsamic glaze, it’s an easy yet impressive dish for entertaining, holiday tables, or a cosy meal at home.

Ingredients

For the Base

• 1 sheet puff pastry, thawed

For the Filling

• 2 large sweet potatoes, thinly sliced
• 2 large onions, thinly sliced
• 1½ tbsp olive oil
• 1 tsp fresh or dried thyme
• Salt and black pepper, to taste
• 5 oz (140 g) Brie cheese, thinly sliced

For the Walnut Honey Crumble

• 1/2 cup (60 g) walnuts, roughly chopped
• 2 tbsp honey
• 1/4 tsp cinnamon
• Pinch of sea salt
• Pinch of red pepper flakes, optional

For Finishing

• Fresh thyme leaves
• 1 tbsp balsamic glaze, optional
• Freshly cracked black pepper

How to Make Sweet Potato & Caramelised Onion Tart

1. Prepare the Oven

Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper.

2. Roast the Sweet Potatoes

Arrange the thinly sliced sweet potatoes on a baking sheet. Drizzle with a little olive oil and season with salt, black pepper, and thyme.

Roast for 12–15 minutes, until slightly tender but still firm enough to arrange on the tart.

3. Caramelise the Onions

Heat the remaining olive oil in a large skillet over medium-low heat. Add the sliced onions and season lightly with salt and black pepper.

Cook for 25–30 minutes, stirring occasionally, until the onions are soft, deeply golden, and caramelised.

4. Prepare the Puff Pastry

Place the thawed puff pastry on the prepared baking sheet. Lightly score a border about 1 inch from the edge without cutting all the way through.

Prick the centre several times with a fork. This helps create a defined border while allowing the centre to bake evenly.

5. Build the Tart

Spread the caramelised onions evenly over the centre of the pastry, keeping the scored border clear.

Arrange the roasted sweet potato slices over the onions, slightly overlapping them.

6. Add the Brie

Place the thinly sliced Brie evenly over the sweet potatoes. Sprinkle with a little fresh thyme.

7. Bake

Bake for 20–25 minutes, until the puff pastry is beautifully puffed and golden and the Brie is soft and melted.

8. Make the Walnut Honey Crumble

While the tart bakes, toast the chopped walnuts in a dry skillet over medium heat for 2–3 minutes.

Reduce the heat and add the honey, cinnamon, sea salt, and red pepper flakes if using. Stir for another 1–2 minutes, until the walnuts are glossy and lightly caramelised.

Transfer the walnut mixture to parchment paper and allow it to cool slightly.

9. Add the Crumble

Remove the tart from the oven and scatter the walnut honey crumble generously over the warm Brie and sweet potatoes.

10. Finish & Serve

Garnish with fresh thyme and freshly cracked black pepper. Add a light drizzle of balsamic glaze if desired.

Slice and serve warm while the pastry is crisp, the Brie is soft and creamy, and the walnut crumble is crunchy.

Tips for the Best Tart

• Slice the sweet potatoes evenly: Similar-sized slices will roast at the same rate and make the tart easier to assemble.
• Cook the onions slowly: Medium-low heat gives the onions time to become deeply golden and caramelised.
• Don’t skip the pastry border: Scoring the pastry creates a neat raised edge around the filling.
• Watch the walnut crumble: Honey can caramelise quickly, so stir the walnuts constantly once the honey is added.
• Add the crumble after baking: This keeps the walnuts crunchy while allowing them to sit over the warm, melted Brie.

Serving Suggestions

This tart is delicious served warm as a vegetarian main dish, appetiser, or side. The combination of sweet potato, caramelised onion, creamy Brie, and crunchy honey walnuts makes it especially suited to autumn and winter gatherings.

A little balsamic glaze and fresh thyme add a final savoury and aromatic touch without overpowering the main ingredients.

Frequently Asked Questions

Can I prepare the onions ahead of time?

Yes. The caramelised onions can be prepared ahead and used when you’re ready to assemble the tart.

Can I leave out the red pepper flakes?

Absolutely. The red pepper flakes are optional and simply add a little contrast to the sweetness of the honey and sweet potatoes.

Can I use dried thyme?

Yes. The recipe works with either fresh or dried thyme.

When should I add the walnut crumble?

Add it after the tart comes out of the oven. This helps preserve its glossy, crunchy texture.

Nutrition & Timing

Details	Amount
Prep Time	25 minutes
Cook Time	45 minutes
Total Time	1 hour 10 minutes
Servings	6
Calories	Approx. 430 per serving
Protein	Approx. 10g per serving

Final Thoughts

Sweet Potato & Caramelised Onion Tart with Brie, Thyme & Walnut Honey Crumble brings together everything you want in a comforting savoury tart: crisp puff pastry, tender sweet potatoes, rich caramelised onions, melted Brie, and a sweet, crunchy walnut topping.

Serve it warm with fresh thyme and a little balsamic glaze for a beautiful centrepiece that’s just as enjoyable for a special gathering as it is for a relaxed meal at home.

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