Description
Grandma’s Onion Squares are a deliciously savory appetizer featuring caramelized onions and a blend of cheeses atop a flaky puff pastry crust. This easy-to-make tart combines sweet, golden onions with creamy sour cream, Parmesan, and mozzarella, baked to perfection and perfect for sharing at any gathering.
Ingredients
Scale
Pastry
- 1 sheet puff pastry (thawed)
- 2 tablespoons unsalted butter
Onion Mixture
- 2 large yellow onions (thinly sliced)
- 1/2 teaspoon salt
- 1/4 teaspoon black pepper
- 1/4 teaspoon dried thyme
- 1/4 cup sour cream
- 1/4 cup grated Parmesan cheese
Topping and Finish
- 1/2 cup shredded mozzarella cheese
- 1 large egg (beaten, for egg wash)
- Chopped fresh parsley for garnish (optional)
Instructions
- Preheat Oven and Prepare Baking Sheet: Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper to prevent sticking and make cleanup easier.
- Caramelize Onions: In a large skillet over medium heat, melt the butter. Add the thinly sliced onions along with salt, black pepper, and dried thyme. Cook slowly, stirring occasionally, until the onions become soft and golden brown, about 15–20 minutes. This slow cooking develops the sweet, rich flavor.
- Mix in Sour Cream and Parmesan: Remove the skillet from heat. Stir in the sour cream and grated Parmesan cheese until combined, creating a creamy, flavorful onion filling.
- Prepare Puff Pastry: On a lightly floured surface, roll out the thawed puff pastry sheet to smooth out creases. Transfer the pastry to your prepared baking sheet. Using a knife, score a 1-inch border around the edges of the pastry, being careful not to cut all the way through. This border will help the edges puff up during baking.
- Assemble the Tart: Spread the caramelized onion mixture evenly within the scored border, distributing it carefully. Sprinkle the shredded mozzarella cheese evenly over the onion layer for a melty, cheesy topping.
- Apply Egg Wash: Brush the beaten egg along the edges of the pastry. This helps the crust develop a beautiful golden-brown color as it bakes.
- Bake: Place the tart in the preheated oven and bake for 18–22 minutes or until the pastry is golden brown and puffed.
- Cool and Serve: Remove from the oven and let cool slightly. Cut into squares and garnish with chopped fresh parsley if desired before serving.
Notes
- For a deeper, richer flavor, take your time caramelizing the onions by cooking them low and slow.
- Try adding crumbled bacon to the onion mixture for a smoky twist.
- Feel free to swap out the mozzarella or Parmesan for other cheeses like Gruyère or cheddar for variation.
- These squares are delicious served warm or at room temperature, making them perfect for parties or casual gatherings.
- Prep Time: 15 minutes
- Cook Time: 25 minutes
- Category: Appetizer
- Method: Baking
- Cuisine: American
