Step 1

In a large bowl, mix together the flour, sugar, salt, and thyme. Add in the cubed butter and toss with a spatula to coat the butter in the flour.

Step 2

Using a pastry cutter, work the butter into the flour until the mixture is a coarse meal. The butter should be about the size of peas.

Step 3

Using a silicone spatula, slowly blend in just enough ice water to form moist clumps.

Step 4

Pour the shaggy dough out onto a clean surface and knead it gently, until it comes together in a ball, adding more ice water only if absolutely needed.

Step 5

Form the dough into a neat ball and gently flatten into a disk.

Step 6

Wrap the disk in plastic wrap and place in the refrigerator to chill for at least 1 hour, or up to 24 hours.

Step 7

Remove the crust from the refrigerator and let it rest for 15 minutes. Lightly flour a rolling pin and a large clean work surface.

Step 8

Set the dough in the middle of the work surface and - beginning from the center of the disc - roll the dough away from you in one firm and even stroke. After each stroke, rotate the disc a quarter turn clockwise and roll again. Lightly sprinkle more flour on the work surface, pie dough, and rolling pin as needed. You want to use just enough to prevent the dough from sticking. As your disc of dough becomes larger, be sure not to overstretch the center of the dough. Continue rolling until the dough is about 16-inches in diameter, and around a 1/4" in thickness.

Step 9

Press the crust into a 9" tart or pie pan, firmly pressing it into the bottom and ridges.

Step 10

Trim excess dough, leaving a ¼” of overhang. Roll the overhand underneath the rim of the pie plate and crimp. Refrigerate for 20 minutes.

Step 11

Preheat the oven to 375 degrees (F).

Step 12

Remove the crust from the fridge. Line the crust with parchment paper and fill with pie weights or dry beans.

Step 13

Bake in the lower third of the oven for 22 minutes. Remove from the oven.

Step 14

Carefully remove the pie weights and parchment paper and prick the bottom of the crust all over with a fork. Place back in the oven and bake for 18 more minutes.

Step 15

In a large skillet over medium-high heat, cook the bacon until crisp and brown, turning it frequently. Transfer to paper towels and drain. Chop and set aside.

Step 16

Return the skillet to the pan. Reduce the heat to medium. Add 1 Tablespoon of the oil, then add the onions and cook, stirring occasionally, until golden brown and caramelized, about 25 minutes. Transfer the onions to a large mixing bowl and set aside.

Step 17

Add the remaining 1 Tablespoon (14ml) of oil to the same pan. Increase the heat to medium-high. Add the mushrooms and cook, stirring occasionally, until they have released their water and begin to brown, about 6 to 8 minutes. Add the onions back to the pan, stir in 1/4 teaspoon of the salt, 1/4 teaspoon of the pepper, mustard and thyme. Cook for 1 minute.

Step 18

Remove the pan from heat and set aside until needed.

Step 19

In a large bowl, whisk the cream, milk, cornstarch, remaining salt and pepper, and eggs until well combined.

Step 20

Reduce the oven temperature to 350 degrees (F).

Step 21

Sprinkle the cheese and bacon on top of the partially baked crust.

Step 22

Top with the mushroom/onion mixture.

Step 23

Pour the egg custard over the top and place in the oven on a large sheet tray.

Step 24

Bake, in the lower third of the oven, until the center is set and the crust is golden brown, about 45 to 50 minutes. If the crust/filling is getting too brown, cover it with a piece of foil but continue cooking.

Step 25

Remove from the oven and cool on a wire rack. Cool for at least 15 minutes before serving warm or cool completely and serve at room temperature.