This is so good. I always serve it as an appetizer during the holidays. Why? Because if you blink twice and the tray is empty. It is a big show stopper! Puff pastry topped with a rich and creamy sauce, crisp bacon, tender cooked onions, and two kinds of cheese on top. I always make more than one tart and leave them to warm in the oven to keep the plate full at all times. Simply delicious!
Caramelized Onion and Cheese Tart
Caramelizing the Onions
1 large sweet onion, Vidalia or sweet yellow onions, sliced thin
2 tablespoons butter
1 tablespoon olive oil
a few sprigs fresh thyme leaves
1-2 tablespoons beef broth
1 teaspoon brown sugar
2 slices bacon, fried and crumbled for topping (optional)
In a large skillet on low-medium heat, melt the butter and olive oil. Add the sliced onions. Cook the onions until they turn a golden brown, stirring often. This will take about 40-45 minutes. Add a little of the beef broth to keep them moist and scrape up the bits on the bottom of the pan.
When the onions are caramelized to a dark golden color, add the onion salt and garlic powder and brown sugar. Stir and cook for about 2 more minutes. Remove from the heat and set aside to cool. If using bacon, add the cooked chopped bacon to your onions now.
Next, prepare your puff pastry dough.
Puffed Pastry Dough
I box (2 sheets) Puffed Pastry
1 tablespoon olive oil
½ cup of shredded Swiss or Gruyere cheese
½ cup finely grated Parmesan cheese
Preheat your oven to 400 degrees. Line a Line a baking sheet with parchment paper.
Unroll a sheet of puffed pastry dough onto a sheet of parchment paper. Gently roll out the puff pastry so that it is a little longer and wider, about 2 inches longer and an inch wider. (Puff pastry is already rolled, but you want it just a little bit thinner.) Brush the entire top with olive oil.
About 1 inch inside the pastry dough, score the edges all the way around (basically making a square inside the dough). I used a knife to do this, but be careful not to cut all the way through the dough. Scoring the dough will allow an edge 'crust' to puff up. You can also simply roll an edge along the sides of the dough and score along the inside edge.
Sprinkle Parmesan cheese all over the inside of the edges. With a fork, pierce the pastry inside your frame several times. Do not pierce the edges.
Bake the puff pastry in the preheated oven for 10 minutes or until it puffs up, and the pastry and cheese are golden brown. It might get quite puffy in the middle, no worries. You can flatten that down.
Remove the pastry from the oven, deflate the center a little bit by piercing it with a fork.
Filling
1/2 cup mayonnaise
1 egg yolk
1/4 teaspoon onion salt
¼ teaspoon garlic powder
black pepper, to taste
3/4 cup shredded Swiss or Gruyere cheese
In a small bowl mix the mayo and egg yolk until well combined. Add the onion salt, black pepper and and garlic powder and stir.
Mix until smooth and creamy.
Gently spread the mixture in the middle of the partially baked pastry staying inside your edges. If the center is too puffy, flatten it a little with your hand before spreading the filling on top.
Next, scoop the onion mixture inside the square in the middle of the puff pastry sheet, spreading it out evenly on top of the filling.
Sprinkle on the shredded Swiss or Gruyere making sure to cover your caramelized onions.
Using a pastry brush, brush the edges of the pastry with the heavy cream. Bake for 23-24 minutes, or until the cheese has melted and the pastry puffs up and is golden brown.
Remove from oven, to a cutting board and cut into squares. Arrange on a serving platter. Top each slice with cooked bacon if desired. Serve immediately and enjoy!
Hints
- Puff Pastry: Take the time to thaw your puff pastry in the fridge, overnight. Open it into a flat piece of dough first. Since you are opening two sheets, go ahead and make two tarts. Keep the puff pastry refrigerated until ready to use. The chilled pastry creates a flaky result.
- Make sure to prick the pastry to prevent from bubbling.
- You may not use all your onions, depending on the size of your onion. Save for later or make a second tart.
I use Vidalia onions when they are available. Otherwise, I use Sweet Yellow Onions. Slice these up into thin, even pieces so that that they cook together at the same time.
Olive Oil: I used regular olive oil and butter to cook the onions in.
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Brown Sugar: This is not only delicious but necessary to get that caramelized glaze on the onions.
Gruyere Cheese: If you don’t have this cheese then you can use Swiss, Sharp white Chedder or even Mozzarella instead
Heavy Cream: This is what you will use to get that golden brown edge on the puff pastry!
Cooking onions: Cooking the onions low and slow is best for bringing out the sweetness. Be patient! Allow the onions to cool for about 10 minutes before assembling.
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