Similar to a quiche, this Onion and Mushroom Tart delivers incredible onion flavor that is accented with intensely flavored sautéed mushrooms finished with a splash of Madeira. It’s perfect for your Mother’s Day brunch or anytime.
It has quickly become an absolute favorite of the Master Taste Tester – so much so that it’s not unusual that we have it several times in a week.
Ingredients for Onion and Mushroom Tart:
The ingredients include a store-bought pie crust, unsalted butter, onions, dried thyme, salt, freshly ground black pepper, mushrooms, Madeira, eggs, and half-and-half. To make an even better Onion and Mushroom Tart, use my Foolproof Pâte Brisée Tart Crust. It used to be that store-bought pie crust worked well. However, recently, it’s been a total disaster, at least for me.
Making the Pastry (or better yet, use my Foolproof Pâte Brisée Tart Crust):
I unrolled the pie crust and placed it in my 9-inch tart pan with a removable bottom. After pricking it with a fork, I put the tart shell in the freezer for 30 minutes. Before baking it, I fitted a crumpled piece of parchment paper on top of the tart shell. Then I filled the tart shell all the way to the top with dried beans to prevent the sides from shrinking down. Into a 375°F oven the tart shell went for 30 minutes. After 30 minutes, I carefully removed the parchment paper and beans. Almost immediately, I noticed that several cracks formed, which is not unusual. To seal the cracks, I brushed the shell with a lightly beaten egg, and placed it in the 375°F oven for another 10 minutes. The last thing that I wanted was for the custard to seep out during baking. The seal worked perfectly!
Cooking the Onions:
Now was the time to make the filling. I started with the onions which I added to melted butter in a 12-inch skillet over medium heat. I added the thyme, salt, and pepper, gave the onions a stir, covered the pan, and cooked the onions over medium heat for about 25 minutes, stirring occasionally. After 25 minutes, depending on the onions, there may be a fair amount of liquid. If so, I used a paper towel to “mop up” the excess liquid. Either way, I cooked the onions for another 5 minutes. I removed the pan from the heat, and let the onions cool.
Cooking the Mushrooms:
Now for the mushrooms – I took the chopped mushrooms by the handful and squeezed as much liquid as I could from them. Then, I placed the squeezed mushrooms in paper towels and continued to squeeze them to remove as much liquid as possible. I’m continually amazed at the amount of liquid in mushrooms! I heated a tablespoon of unsalted butter in a 10-inch skillet over high heat and added the mushrooms. After about 2 minutes of stirring the mushrooms constantly, I added the Madeira and continued stirring the mushrooms until most of the liquid had evaporated. This took another 2 minutes. I removed the pan from the heat to allow the mushrooms to cool.
Making the Filling:
Now for the filling – I whisked the eggs and half-and-half and stirred in the onions and mushrooms. I poured the onion/mushroom mixture into the tart shell and placed it into a preheated 375°F oven for 25 minutes until the center felt firm to the touch.
After 25 minutes, the Onion and Mushroom Tart was perfectly cooked. I let it cool for about 10 minutes before cutting into it. With its incredible onion flavor accented with an intensely flavored sautéed mushroom, the Onion and Mushroom Tart was absolutely delicious. Yum!