Savory Caramelized Onion, Mushroom and Thyme Tart

  • Author: The Kitchen Whisperer

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  • Homemade crescent roll dough or 2 cans of pre-made crescent roll dough
  • 1 large vidalla onion cut into 1/4” slices
  • 1 pound of mushrooms (baby bella or button), cleaned and sliced in halves or thirds
  • 1 tablespoon + 1 teaspoon fresh thyme
  • 1 tablespoon butter
  • 1 tablespoon extra virgin olive oil
  • 1 tablespoon flour (optional)
  • 1 teaspoon kosher salt
  • 1/2 teaspoon ground black pepper
  • 12 cups fresh grated cheese (smoked mozzarella, gruyere, fontina, etc..)


  1. Put a large skillet over medium high heat.
  2. Add in the butter and olive oil until the butter is melted and just starts to buttle.
  3. Add in the onions and stir to coat the onions with the butter oil.
  4. Spread the onions out evening and let cook, stirring occasionally.
  5. Reduce the heat to medium/medium low to prevent the onions from drying out and or burning.
  6. After 10 minutes sprinkle with1/2 teaspoon of salt and pepper.
  7. Cook for about 15-20 minutes or until the onions start to caramelize and turn a gorgeous brown color.
  8. Add in the mushrooms and stir to combine.
  9. Cook for 10 minutes or until the mushrooms are soft and cooked. If it seems to be bit dry, add in a teaspoon of butter.
  10. When the mushrooms are cooked, add in 1 tablespoon thyme and remaining salt and cook for 1 minute.
  11. If there is still liquid in the pan, add in the flour and stir to thicken.
  12. Remove from heat and allow to just cool.
  13. While cooling, preheat the oven to 375F.
  14. Line a baking sheet with parchment paper and spray with cooking spray.
  15. Place your dough on the parchment paper and roll out to a 12×16” shape (or the size of your pan). You want the dough to be about 1/4” thick. *If you’re using canned dough, it’ll be 1 1/2 cans worth. You’ll keep the remaining 4 triangles for decorations.
  16. Add the grated cheese on the bottom of the dough leaving a 1-1 1/2” edge.
  17. Add the cooled onion mushroom mixture over top of the cheese spreading it out as evenly as possible.
  18. Starting in one corner, gently fold up an edge of the dough onto the onion mushroom mixture.
  19. Continue all the way around the tart folding up the edges of the tart to help seal it in (the middle is still exposed). As you move around the tart folding up the edges, gently pinch it down almost creating a pleated effect.
  20. To decorate take the remaining dough and make ‘ropes’ out of the dough and add them as criss-crosses to it. Or you could not roll it and use a cookie cutter to create shapes and place them onto the tart.
  21. Bake for 15-17 minutes or until the dough is golden brown and just crisp.
  22. Cool on the pan for 1 minute and then using a large spatula, remove it from the parchment paper and cool on wire rack for a 5 minutes (if you’re going to eat right away) or until room temp. This can be served room temp or hot.


Like Bacon? Okay seriously, like who doesn’t? LOL Fry up 6 slices of bacon. Break up into pieces. Instead of the butter and olive oil above, caramelize the onions in the bacon grease.

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