Caramelized Onion and Radicchio Quiche

1. Bake the Crust

Preheat your oven to 375°F. Roll out the Perfect Piecrust dough and gently press it into your pie pan. Line the crust with foil and fill it with pie weights or dried beans to prevent bubbling. Bake the crust for 20 minutes, then carefully remove the weights and foil and bake for an additional 5 to 7 minutes until the crust is lightly golden.

2. Seal and Flavor the Crust

Once the crust is ready, brush it with a large egg white to create a barrier that will help keep the crust crisp. Sprinkle 3 tablespoons of grated Gruyère cheese over the crust. Return it to the oven for 10 to 13 minutes. This step not only seals the crust but also adds a delightful flavor from the melted cheese.

3. Caramelize the Onions

While the crust is baking, heat 2 tablespoons of extra-virgin olive oil in a large pan over medium heat. Add one large red onion, halved and thinly sliced. Season with ½ teaspoon of kosher salt and ¼ teaspoon of sugar. Cook the onions for about 15 minutes, stirring occasionally, until they become soft and caramelized.

4. Cook the Radicchio

Next, stir in a medium radicchio, halved and thinly sliced, along with 1 tablespoon of olive oil and ¼ teaspoon of kosher salt. Cook for another 10 minutes until the radicchio wilts. Add a teaspoon of balsamic vinegar, stirring for an additional minute to let the flavors meld.

5. Prepare the Custard

In a medium bowl, whisk together 3 large eggs, 1½ cups of heavy cream, ¼ teaspoon of freshly grated nutmeg, ¾ teaspoon of kosher salt, and ½ teaspoon of freshly ground black pepper to form the custard mixture.

6. Assemble and Bake the Quiche

To assemble the quiche, spread half a cup of the radicchio-onion mixture evenly over the baked crust. Pour the custard mixture over the top, making sure it covers the filling. Dot the surface with 1 tablespoon of cubed unsalted butter, and sprinkle a pinch of fleur de sel for a final touch of seasoning. Place the quiche in the oven and bake for 25 to 35 minutes, until the custard is puffed and golden. Look for a slight jiggle in the center—this indicates the custard is perfectly set but still creamy. Once done, let it cool slightly before serving.