Preheat the oven to 350 F (180 C).

Lightly grease an 8″ (20 cm) square mold and line it with parchment paper.

For the crust:
Mix the flour and sugar.
Incorporate the butter with your fingers or a pastry blender until the dough has a coarse and crumbly texture (it will look dry).
Add the Cheddar to the dough and press the dough into the prepared mold.
Bake for 12 minutes and let cool to room temperature.

For the filling:
Keep the oven at 350 F (180 C).
Heat the oil in a large skillet over medium heat and cook the shallot and mushrooms until the mushrooms have completely released their water (about 6 minutes).
Then add the garlic and thyme, and season lightly with salt and pepper.
Remove the skillet from the heat and let cool.

Whisk the eggs and cream in a large bowl.
Add the mushroom mixture, cooked bacon, and Cheddar.
Pour the filling over the cooled crust and bake until the center of the filling no longer moves (about 30 minutes).
Let cool to room temperature, then refrigerate for at least 4 hours before cutting into squares.

The squares can be served at room temperature or warmed for 10 minutes at 350 F (180 C) on a baking sheet.