French Onion Soup Tart
French onion soup in tart form - what could be better? A flakey rough puff pastry base, melty cheese, and savory caramelized onions on top - yum!
Ingredients
- 2 tbsp oil (for cooking)
- 1 kilogram medium-sized yellow onions
- Water, as needed
- 1 tsp "better than bouillon"; beef flavored (or 1/2-1 cube of beef bouillon, beef seasoning)
- 1 tbsp fresh thyme, chopped (substitute with dried thyme, but reduce to 1 tsp!)
- 226 grams gruyere cheese, grated
- Pepper to taste
- Grated parmesan (for garnishing the tart, this is optional!)
- Fresh thyme (for garnish; optional)
- 1 egg (for egg wash)
- 1 portion rough puff pastry (The pastry portion of this recipe was adapted from Sally's Baking Blog)
Instructions
- Make the rough puff pastry at least 2.5 to 3 hours ahead of time; follow the steps in our recipe! You can make this recipe much easier by using a sheet of storebought pastry, making sure to follow the instructions on the package for thawing!
- While the dough is resting for the two hour period, we like to start the process of caramelizing the onions. You can also do this after you've finished the dough and it's resting for the last time in the fridge if you'd like!
- Peel your onions and cut them in half. Slice all the halves.
- Add the onions to a cast iron skillet, dutch oven, or a pot with a large base along with a few tablespoons of oil.
- Cook on low-medium heat for around an hour, stirring occasionally. Add water as needed to stir up any bits that are sticking to the bottom of the pan.
- Once the onions have become a deep golden color, stir in 1 tbsp of fresh thyme (or 1 tsp dried thyme) and add beef bouillon. We use "better than bouillon," the roasted beef version, to get that beef flavor of French onion soup. You can use whatever beef flavored bouillon/seasoning you like! Ours is plenty salty after this, but make sure to taste and add extra salt if needed!
- Set the onions aside to cool slightly before using. You can also put them in the fridge if you're making them ahead of time.
- Continue laminating the dough based on our recipe, and make sure it has a final rest in the fridge.
- Preheat your oven to 400F (204C).
- Grate the gruyere cheese.
- Once the dough has rested, roll it out on a floured surface to a rectangle measuring about 10" by 15".
- Transfer the rectangle to a parchment lined baking sheet. We roll up the dough around the rolling pin, then unroll it over the parchment to transfer it easily.
- Spread grated gruyere cheese across the dough, leaving at least a 1" border around all the edges.
- Add caramelized onions in an even layer across the cheese; make sure the 1" border remains.
- Fold up 1/2" of the dough around the edges to create a thicker crust. You may want to brush the edges with water or an egg wash to get it to stick a little better!
- Crimp with a fork to ensure that it doesn't unfold.
- Egg wash the edges of the pastry. An egg wash is one egg with a little bit of water, whisked together in a bowl. Use a pastry brush to spread the mixture onto the pastry edges.
- Bake the tart for around 30 minutes or until the pastry has puffed up around the edges, and is golden brown. Remove from the oven, transfer to a wire rack, and let cool for at least 15 minutes.
- Add grated parmesan across the top of the tart (optional). Add fresh ground pepper to the top as well, along with some sprigs of fresh thyme (also optional).
- Slice and enjoy! Store in the fridge for 2-3 days and reheat in the oven/toaster oven for best results.
