Puff Pastry Breakfast Tart with Asparagus and Gruyère

Why You’ll Love This Recipe

• Golden, ultra-flaky puff pastry meets creamy Gruyère and sweet, jammy onions.
• Asparagus and soft-set eggs make it a complete, elegant breakfast in one pan.
• Smart make-ahead move: caramelize the onions in advance to streamline brunch.
• Versatile and impressive—great for brunch, a light dinner, or entertaining.

Grocery List

• Produce: 2 medium yellow onions, 1 bunch thin asparagus, fresh chives
• Dairy: All-butter puff pastry (1 sheet), Gruyère cheese, eggs, milk or cream (optional)
• Pantry: Olive oil, unsalted butter, kosher salt, black pepper, flaky sea salt, balsamic vinegar (optional)

Full Ingredients

Puff-Pastry Tart

• 1 sheet (250 g) all-butter puff pastry, thawed until pliable but still cold
• 1 tbsp (14 g) unsalted butter
• 4 tsp (20 ml) olive oil, divided
• 2 medium yellow onions (about 1 lb/450 g), thinly sliced
• 12 oz (340 g) thin asparagus, woody ends trimmed
• 4 oz (113 g) Gruyère, coarsely shredded (about 1 packed cup)
• 4 large eggs
• 3/4 tsp kosher salt, divided
• 1/2 tsp freshly ground black pepper
• 1 tbsp milk or cream, for brushing the pastry border (optional)

To Finish

• 2 tbsp finely snipped fresh chives
• Flaky sea salt, for serving
• Optional: 1 tsp balsamic vinegar or 1 tbsp water for deglazing onions

Step-by-Step Instructions

Step 1: Preheat and thaw pastry

Heat the oven to 400°F (200°C) with a rack in the center. If your puff pastry is frozen, thaw it at room temperature until pliable but still cool (30–40 minutes). Keep the pastry in the refrigerator once pliable so it stays cold while you prepare the toppings.

Step 2: Caramelize the onions

In a large skillet over medium-low heat, melt the butter with 3 tsp of the olive oil. Add the sliced onions and 1/2 tsp kosher salt. Cook, stirring every few minutes, until the onions are deep golden and jammy, 25–30 minutes. If brown spots form, add 1–2 tsp water to deglaze and reduce the heat slightly. Optional: stir in 1 tsp balsamic vinegar at the end for brightness. Set aside to cool slightly.

Step 3: Prepare the pastry base

Line a rimmed baking sheet with parchment. On the parchment, unfold or roll the puff pastry to about 10×14 inches (25×35 cm). Using a knife, lightly score a 1-inch (2.5 cm) border around the edges, taking care not to cut all the way through. Dock the center all over with a fork to prevent excessive puffing. Brush the border with milk or cream (optional) for color. Slide the whole sheet into the fridge for 10 minutes to rechill.

Step 4: Par-bake the pastry

Bake the pastry for 12 minutes, until lightly golden and set. If the center puffs, gently press it down with the back of a spoon while it’s hot. Keep the border intact and puffed.

Step 5: Layer cheese, onions, and asparagus

Sprinkle the Gruyère evenly over the center inside the border. Spoon the caramelized onions over the cheese in an even layer. Toss the asparagus with the remaining 1 tsp olive oil, 1/4 tsp kosher salt, and the black pepper. Arrange the spears attractively over the onions, pointing in the same direction or in a herringbone pattern.

Step 6: Add eggs and bake until just set

Use the back of a spoon to create 4 shallow wells, spaced apart. Crack the eggs one at a time into a small cup, then slide each into a well. Return the tart to the oven and bake 10–12 minutes, until the whites are just set but the yolks are still soft and slightly wobbly. For firmer yolks, add 1–2 minutes. Rotate the pan halfway if your oven browns unevenly.

Step 7: Finish and serve

Let the tart rest for 5 minutes to allow the eggs to settle. Shower with the chives and a pinch of flaky sea salt. Slice into 4–6 pieces and serve warm.

Pro Tips

• Keep the pastry cold until it hits the oven for the flakiest layers; a quick 10-minute chill after scoring works wonders.
• Use thin asparagus so it cooks through as the eggs set. If your spears are thick, peel the lower halves.
• Crack eggs into cups first for cleaner placement and fewer broken yolks.
• If the border browns too fast, tent the edges loosely with foil during the final minutes.
• Make the onions up to 5 days ahead; they’re the time-saver that streamlines brunch.

Variations

• Mushroom–Thyme: Sauté 8 oz sliced cremini with thyme and fold into the onions; proceed as directed.
• Prosciutto–Arugula: After baking, drape 4–6 thin slices prosciutto over the tart and finish with a handful of arugula and a squeeze of lemon.
• Tomato–Basil: Swap asparagus for halved cherry tomatoes; finish with basil instead of chives.

Storage & Make-Ahead

The tart is best just baked, while the pastry is crisp and the yolks are soft. Leftovers keep covered in the refrigerator for up to 2 days; reheat at 350°F (175°C) on a baking sheet for 8–10 minutes. Avoid microwaving, which softens the pastry. Make-ahead: caramelize onions up to 5 days in advance (refrigerate, then warm slightly before using). You can also par-bake the pastry base up to 6 hours ahead; cool, cover, and keep at room temperature. Assemble and bake with eggs right before serving.

Nutrition (per serving)

Approximate values for 1/4 tart: 580 calories; 22 g protein; 34 g carbohydrates; 38 g fat; 2 g fiber; 680 mg sodium. Values will vary with brands and exact ingredients.