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Caramelized Onion Puff Pastry Quiche

Caramelized Onion Quiche
Serves: 6 People
5 from 2 votes
Prep Time1 hr
Cook Time40 mins
Total Time1 hr 40 mins


  • 1 sheet puff pastry thawed but cold if frozen, let thaw in the fridge for 24 hours
  • 4 tbsp olive oil, plus additional as needed (see below)
  • 1 large yellow onion, halved and thinly sliced
  • 1 tsp Kosher salt
  • 4 large eggs
  • 1 + 1/4 milk whole milk
  • 1 cup grated gruyere cheese
  • 1 tbsp dijon mustard
  • 2 cloves garlic minced
  • 2 cups sliced shiitake mushrooms, stem removed, sub baby bella mushrooms
  • ¼ tsp freshly ground black pepper
  • 2 cups swiss chard, stem removed and thinly sliced into ribbons (about 1 bunch)
  • 1 tsp fresh thyme leaves, finely chopped


Caramelize the Onions

  • Begin by caramelizing your onions. In a large skillet over medium heat, add 2 tbsp of the olive oil, onion and ½ tsp salt. Saute, stirring occasionally, until the onions are golden brown and caramelized, about 35-45 minutes. If your onions start to look slightly dry, add a drizzle of olive oil as needed. If they seem to be browning too quickly, adjust heat to medium-low.
  • After about 35 minutes of the onions cooking, start making the rest of your filling.

Make your Filling

  • In a large bowl, add the eggs, milk, cheese and Dijon mustard. Whisk to combine and set aside.
  • Once your onions are done cooking, remove from the heat and set aside to cool.
  • In the same pan used for the onions, add 2 tbsp olive oil, garlic, mushrooms and ½ tsp salt. Saute, stirring, until the mushrooms have softened, about 2-3 minutes.
  • Add the swiss chard and stir to combine, let cook for another 1-2 minutes until the swiss chard has slightly softened. Set aside to cool.

Assemble the Quiche

  • Preheat your oven to 400 degrees F and lightly grease your pie dish.
  • Roll the puff pastry sheet out to larger than the size of your pie plate. Press the pastry into the dish, folding over and gently stretching until it fits your dish, trimming if desired.
  • Once your veggies are cooled, add to your egg mixture and stir to combine. Next add the thyme and mix again then pour into your pan.
  • Pour the filling into the pastry. Bake, uncovered, until the filling is set and the crust is golden brown, 35-45 minutes. (if the top is starting to look overly browned, tent with a piece of foil.)
  • You want your eggs to be set; however, you want it to have a bit of a wobble to it as it comes out of the oven. It continues to cook and set as it rests and the wobble will ensure it has a silky, not rubbery, texture.
  • Remove from the oven and let cool for 5-10 minutes before slicing. Serve and enjoy!


For the Caramelized Onions: To save time the day of your brunch, I recommend caramelizing your onions the day before! Cook according to the recipe instructions, allow them to cool completely then store in an airtight container in the fridge until you are ready to make the filling the day of your brunch.