Mushroom Tart

Mushroom Tart

River City Shiitake

I had the incredible pleasure of visiting River City Shiitake here in Portland, OR with my friends from New Seasons Market. Mary, the lead mushroom cultivator at River City Shiitake shares her experience of pressing her own “blocks” to grow some of the most delicious shiitake and maitake mushrooms in the area.

Woman holding Mushroom Tarts

This post is sponsored by New Seasons Market. All ideas and opinions are my own.

Pressing “Blocks”

Besides finding mushrooms in the forest, I have never really seen the process of cultivating mushrooms in large quantities. “Blocks”, as Mary calls them are created from a mixture of millet, saw dust and wheat grain. This mixture (varies on mushroom) are then put into a giant pressure cooker to sterilize the “blocks” for 3-3.5 hours.

The blocks are then placed in a sterile room and finally the cultivation process begins with mycelium, the seed/root of a mushroom. The process for shiitake mushrooms takes a full 16 weeks of inoculation. The mycelium begins the process of creating the mushrooms in bags. The mushrooms begin their cultivation process in a climate controlled room and monitored regularly.

I am still in awe and only know a fraction of how this process all works. It was absolutely fascinating learning this extensive process to create some of the best mushrooms around. River City Shiitake provides about 90% of their shiitake and maitake mushrooms to New Seasons Markets. Truly a local farm bringing the best produce to small markets.

Benefits of Mushrooms

Shiitake mushrooms specifically have been cultivated for hundreds of years and no doubt have health/medicinal benefits. Some quick facts on the health benefits, more can be found here.

  • Contain calcium ~ great for bones
  • Antioxidants that help fight free radicals
  • Great for digestion as they contain high amounts of fiber
  • Help manage diabetes by breaking down sugars in our bodies

Of course, having a few shiitakes won’t necessarily cure us of all these things but incorporating into our regular diet will certainly help.

Mushroom Tart

My favorite way to consume mushrooms isn’t in a supplement but rather eating them, preferably with a lot of butter, salt and herbs! I love the meaty texture and ability to create a stunning dish. They are absolutely perfect for soups, like my Creamy Mushroom Soup or in this delicious and elegant tart.

Tart Components

The quintessential tart must ultimately begin with a flaky and delicate crust. I prefer an all butter crust because, well, butter is AMAZING. I choose to use New Season’s European Style Butter which contains more fat and less milk. I’ve enhanced my crust with some lemon zest and garlic but if you’re pinched for time, you can certainly buy a good pre-made pie crust from your local New Seasons Market. Some other ingredients you’ll need for this tasty dish include:

  • shiitake and/or maitake mushrooms
  • onions
  • Parmesan cheese
  • heavy cream
  • eggs
  • parsley
  • thyme
  • lemon
  • garlic
  • butter
  • olive oil
  • 11″ tart pan

Roasting the mushrooms with a good amount of butter, olive oil and salt bring them to life. Giving them a nice meaty texture that will shine through in your tart. This will also keep mushrooms in tact to place on top of your tart to showcase their beauty.

A layer of caramelized onions, Parmesan cheese and finally a custard filling to set it all together creates an unbelievable texture and meal perfect for breakfast, lunch or dinner. And even better for a holiday get together. Make in the morning have it ready as it’s best served warm or room temperature.

Serve with a lovely peppery arugula salad simply dressed with lemon juice and olive oil or enjoy as is.

Mushroom Tart
Perfect to serve for a brunch.

As always, I love seeing your creations. Please leave a review or share your dish with me on social media. You can find me on Facebook, Instagram, Twitter and Pinterest. For more delicious recipes to your inbox, sign up for my newsletter!


Mushroom Tart
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Mushroom Tart

  • Author: Cosette’s Kitchen
  • Prep Time: 30 minutes
  • Cook Time: 50 minutes
  • Total Time: 1 hour 20 minutes
  • Yield: 8 slices 1x
  • Category: tart
  • Method: baking
  • Cuisine: french, american


A delicious savory tart, enjoy for breakfast, lunch or dinner.

Adapted from Epicurious recipe



All-Butter Herby Crust

  • 2 cups all-purpose flour
  • 1.5 Tbsp sugar
  • 1/2 tsp kosher salt
  • zest of 1 lemon
  • 1 clove of garlic
  • 2 sprigs of thyme
  • 3/4 cup unsalted New Seasons European butter (1.5 sticks), cold and cut in pieces
  • 610 Tbsp ice cold water

Tart filling

  • 1 pound of assorted shiitake/maitake mushrooms
  • 6 Tbsp olive oil, divided, additional as needed
  • 2 Tbsp New Seasons European butter
  • 1 cup shredded Parmesan cheese
  • 2 large onions, thinly sliced
  • 1 1/3 cup heavy cream
  • 2 eggs
  • 1/4 cup chopped parsley
  • 23 sprig of thyme
  • kosher salt + pepper


All-Butter Herb Crust

  1. In the bowl of a food processor, add your flour, sugar, salt, garlic clove, lemon zest and thyme and pulse for a few seconds until combines and garlic clove is broken up.
  2. Add in your cut pieces of cold butter and pulse a few times.
  3. Add in 4-6 Tbsp of ice cold water (I add ice to my measuring cup I scoop out of)
  4. Pulse a few more times, add additional water until a crumbly but slightly cohesive dough comes together when pinched together between fingers.
  5. Dump your pie dough in your 11″ tart pan and begin pressing into place. I like to use a tart press or a measuring cup to create an even layer of dough along the bottom and then press my fingers along the edges.
  6. Continue pressing into place until you have an even bottom and edges that go along the sides.
  7. Place in fridge for at least 30 minutes.
  8. Preheat oven to 425 degrees.
  9. After 30 minutes, place tart pan on sheet pan (important so it doesn’t leak in your oven) and prick with a few holes using a fork. Bake your shell for 20 minutes until it pre-bakes (you will roast mushrooms at the same time). Remove and let cool, drop temperature to 375 degrees.

Tart Filling

  1. Place your mushroom in a single layer on a sheet pan and coat with 4 Tbsp of olive oil (or more, you want them coated). Mix until all pieces are coated in olive oil then season with kosher salt. Dot the top of the mushrooms with 2 Tbsp unsalted butter and roast for 15-20 minutes at 425 degrees. Set aside. (roast at same time as pre-baking tart crust)
  2. In a large skillet, add your additional 2 Tbsp of olive oil and heat on medium-high. Add your sliced onions and begin cooking stirring consistently. Allow the onions to soften and become translucent and slightly browned. Process should take 10-12 minutes, set aside.
  3. In a large measuring cup or bowl whisk together your heavy cream, eggs, parsley, 1/2 tsp kosher salt and several grinds of black pepper.
  4. Begin assembling your tart.
  5. Place your caramelized onions on the bottom of your cooled tart shell, then add your shredded Parmesan cheese, next pour your heavy cream mixture and finally top with your roasted mushrooms, pressing them in slightly and add some additional thyme leaves.
  6. Cover your tart pan with foil and set back on baking sheet. Bake for 25 minutes at 375 degrees. After 25 minutes, remove the foil and bake for another 25 minutes until the center is set and top is golden brown. Top with additional thyme or greens.
  7. Allow tart to cool to warm or room temperature. Slice and enjoy!


  • If you are using table salt, use sparingly as it has a higher salt flavor than kosher/flake
  • You may prepare your tart shell, mushrooms and onions the day before baking to help speed up the process. Refrigerate until ready to assemble.
  • Make the day before and heat up in the oven on a low temperature.

Keywords: mushroom tart, tart, pie, savory, mushroom, shiitake, brunch, breakfast, lunch, dinner, mushroom, quiche

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