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Baking recipe · from the recipe book

Caramelized Onion, Mushroom and Thyme Tarts

Jammy onions and browned mushrooms set in a creamy ricotta-Parmesan custard over a crisp, buttery press-in crust flecked with thyme.

Caramelized Onion, Mushroom and Thyme Tarts

Ingredients

  • 2¾ cups340 gAll-purpose flour
  • 1 cup200 gUnsalted buttermelted, then divided
  • ¾ cup grated80 gGrated Parmesandivided
  • 1 tbsp3 gDried thymedivided
  • 1 tsp6 gSaltdivided
  • 3 tbsp45 gWatercold
  • 4½ medium500 gYellow onionthinly sliced
  • 6½ cups sliced450 gWhite mushroomssliced
  • 3 cloves9 gGarlicminced
  • 1½ tbsp20 gOlive oil
  • 5 large250 gEggs
  • 1 cup250 gPart-skim ricotta
  • ¾ cup (180 ml)200 gWhole milk
  • ¾ tsp2 gBlack pepper
  • 2½ tbsp chopped10 gFresh parsleychopped

Steps

  1. Heat the olive oil in a large skillet over medium-low heat. Add the onion and cook, stirring often, until deep golden and jammy, about 30 minutes.
  2. Meanwhile, make the crust: in a bowl, stir the flour, half the Parmesan, half the thyme and half the salt. Pour in 180 g of the melted butter (all but about 1 tablespoon) and the cold water, and stir into a crumbly dough that holds together when squeezed.
  3. Divide the dough in half and press each half evenly over the bottom and up the sides of a 9-inch tart pan. Prick the bottoms with a fork and chill the shells for 20 minutes.
  4. Preheat the oven to 375°F (190°C). Bake the chilled shells for 15 minutes until lightly golden, then set aside.
  5. When the onion is done, raise the heat to medium-high, add the remaining melted butter and the mushrooms, and cook until browned and their liquid evaporates, about 8 minutes. Stir in the garlic and the remaining thyme for 1 minute, then let cool slightly.
  6. In a bowl, whisk the egg, ricotta, milk, the remaining Parmesan, the remaining salt and the black pepper until smooth.
  7. Divide the onion-mushroom mixture between the baked shells, then pour half the custard into each.
  8. Bake at 375°F (190°C) for 30 to 35 minutes, until the centers are just set and reach 160°F (71°C).
  9. Cool the tarts on a rack for 20 minutes, sprinkle with the parsley, and cut each into 6 slices.

Food safety: Don't taste raw dough or batter: raw flour and raw eggs can carry germs.

Contains: Milk, Egg, Gluten.

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Saved in the Every Helping recipe book on October 24, 2026.

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