Upside-Down Onion and Gruyere Tarts are a fantastic and relatively easy appetizer that combine the sweetness of caramelized onions with the nutty, savory flavor of Gruyère cheese, all on a flaky puff pastry base. Here’s a general recipe, drawing on common elements from various sources:
Yields: 6-9 tarts Prep time: 15-20 minutes Cook time: 20-25 minutes
Ingredients:
- 1 sheet puff pastry, thawed (follow package directions for thawing, usually in the fridge overnight or at room temperature for 40 minutes)
- 1 medium yellow or white onion, thinly sliced (about 1/8 inch thick, or use smaller onions/shallots)
- 2-3 tablespoons honey (or hot honey for a kick, or balsamic glaze)
- 100-150g Gruyère cheese, grated or thinly sliced (about 1.5 – 2 cups shredded)
- Fresh thyme leaves, about 1-2 tablespoons (or dried thyme, about 1 teaspoon)
- Salt and freshly ground black pepper, to taste
- 1 large egg, beaten (for egg wash)
- Optional: 1-2 tablespoons olive oil, for drizzling
Equipment:
- Baking sheet
- Parchment paper
- Pastry brush (optional)
Instructions:
- Preheat Oven and Prepare Baking Sheet: Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper. This is crucial for easy flipping and preventing sticking.
- Prepare the Base:
- On the parchment-lined baking sheet, drizzle small amounts of honey (or balsamic glaze/olive oil, depending on your preference) creating 6-9 separate “pools” for each tart. Space them out evenly.
- Sprinkle fresh thyme leaves, a pinch of salt, and a grind of black pepper over each honey pool.
- Layer the Onions and Cheese:
- Place a slice or a small cluster of thinly sliced onion on top of each seasoned honey pool. If your onion slices are large, you might use one per tart. If they are smaller, you can arrange a few to cover the area.
- Top the onions with a generous handful of grated Gruyère cheese or a few thin slices. The cheese will melt and help bind the onions.
- Prepare the Puff Pastry:
- Unroll the thawed puff pastry. Lightly flour your work surface if needed and gently roll the pastry slightly to ensure it’s even.
- Cut the puff pastry into 6-9 equal rectangles or squares, sized to fit over your onion and cheese stacks.
- Assemble the Tarts:
- Carefully place one puff pastry rectangle on top of each onion and cheese stack. Gently press down around the edges of the pastry to seal it somewhat and create a “cup” around the filling.
- Egg Wash and Bake:
- In a small bowl, whisk the egg with a splash of water (about 1 tablespoon) to create an egg wash.
- Brush the top of each puff pastry tart with the egg wash. This will give them a beautiful golden-brown color and a flaky finish.
- Bake for 20-25 minutes, or until the puff pastry is puffed up, golden brown, and the onions are softened and slightly caramelized, and the cheese is bubbly.
- Flip and Serve:
- Remove the tarts from the oven. Let them cool on the baking sheet for about 1-2 minutes. This helps the honey and cheese to set slightly.
- Using a spatula or offset palette knife, carefully flip each tart over onto a serving plate. The caramelized onions and melted Gruyère will now be on top, creating the “upside-down” effect.
- Serve warm. These are best enjoyed on the same day they are made, but leftovers can be reheated gently in the oven.
Tips and Variations:
- Caramelized Onions (Optional but Recommended): For a deeper flavor, you can caramelize the onions in a skillet with a little olive oil and butter before assembling the tarts. This takes extra time (30-45 minutes on low heat, stirring occasionally), but results in incredibly sweet and tender onions. If you do this, let them cool before assembling.
- Other Cheeses: While Gruyère is classic, you can experiment with other cheeses like sharp cheddar, fontina, or even goat cheese for a different flavor profile.
- Additions: Consider adding a sprinkle of balsamic vinegar, a dash of garlic powder, or a thin slice of cooked bacon or ham to the onion layer for extra flavor.
- Don’t Overcrowd: Ensure you leave enough space between the tarts on the baking sheet for them to puff up properly.
- Storage: Store leftovers in an airtight container in the fridge for up to 1 day. Reheat in the oven at a low temperature to crisp up the pastry.
Enjoy your delicious Upside-Down Onion and Gruyere Tarts!