In a mixing bowl, combine the flour, salt, and sugar.

Add the softened butter. Using your fingers, rub the butter into the flour until the mixture resembles coarse breadcrumbs. (Pro-tip: Do not let the mixture get too warm, or the butter will separate).

Add the egg and lightly mix it into the dough.

Gradually sprinkle in the ice-cold water, just enough until the dough comes together into a cohesive ball. Do not over-knead.

Cover the dough and let it rest at room temperature for 10 minutes.

Preheat your oven to 180°C (350°F).

Lightly brush your tart molds with melted butter (or line them with parchment paper).

Place the dough between two sheets of plastic wrap and roll it out to about ½ centimeter (¼ inch) thick.

Place the molded crusts briefly into the freezer to firm up.

Remove from the freezer and prick the bottom of the dough a few times with a fork.

First Bake: Line the inside of each crust with a small circle of parchment paper and fill with dried chickpeas (to weigh the dough down and prevent puffing). Bake at 180°C (350°F) for 8 minutes.

Second Bake: Carefully remove the parchment paper and chickpeas. Lower the oven temperature to 170°C (340°F) and bake the empty crusts for another 8 minutes until lightly golden and sealed.

The Custard: In a bowl, add the crème fraîche (or heavy cream), white pepper, nutmeg, and salt. Crack in 2 eggs and whisk gently just to break them up and combine. Stir in the grated Parmesan and Emmental cheeses. Set aside.

Sautéed Mushrooms: Heat a skillet over high heat. Add the olive oil and the smashed garlic cloves to flavor the oil. Let the garlic turn golden.

Drop the mushrooms into the hot pan. Do not stir immediately. Let them sit until the bottoms get a nice seared color (this prevents them from releasing too much water). Toss them slightly, then season with dried thyme, black pepper, and a pinch of salt. Remove from heat and set aside.

Keep the oven at 170°C (340°F).

To make the Mushroom Quiche:

Spread a very small amount of caramelized onions on the bottom of a baked tart shell.

Add a layer of the sautéed mushrooms.

Pour the custard and cheese mixture over the top until the shell is full.

To make the Caramelized Onion Quiche:

Add a generous, thick layer of caramelized onions to the bottom of a baked tart shell.

Pour the custard and cheese mixture over the onions until full.

Place the assembled quiches into the oven at 170°C (340°F).

Bake for 12 to 15 minutes (for the mushroom) and 15 to 20 minutes (for the onion), or until the custard is set and the tops are beautifully golden brown.

Remove from the oven and allow them to cool before carefully removing them from the tart molds.

Garnish the onion quiche with a tiny bit of extra caramelized onion on top.

Slice in half and enjoy the perfect crumbly, savory, and sweet balance!