In a large skillet over medium heat, heat a couple of tablespoons of olive oil. Add 2 cups of sliced onions and sauté until they become soft and translucent, about 10-15 minutes. Once softened, reduce the heat to low, add a splash of water to prevent sticking, cover, and continue cooking until they turn a rich golden brown, roughly 50 minutes in total.

Preheat your oven to 350°F (180°C). Toss 2 cups of peeled and diced squash with olive oil, salt, and pepper, ensuring they're well-coated. Spread the squash in a single layer on a baking sheet and roast in the preheated oven for about 30-40 minutes or until tender and lightly caramelized, stirring halfway through for even cooking. Remove and set aside.

While the squash roasts, prepare the crust by brushing a sheet of phyllo dough with olive oil and layering it in a greased 9-inch pie or springform pan. Repeat this process with 7 more sheets, arranging and tucking the overhanging ends around the edge of the pan to create a lovely, fluted design.

In a mixing bowl, combine the beautifully caramelized onions, roasted squash, 4 lightly beaten eggs, 1 cup of half-and-half, crumbled Gorgonzola, and thinly sliced sage. Stir thoroughly until well-combined, then pour the mixture into the prepared phyllo crust, ensuring it's distributed evenly.

Place the quiche in the preheated oven, set to 375°F (190°C), and bake for 25-45 minutes. The quiche is done when the filling has set firmly in the center and the edges are golden brown.

Once baked, remove the quiche from the oven and allow it to cool for about 10-15 minutes before slicing.