Place the bulgur in a medium bowl and cover with 1 1/2 cups boiling water. Let it soak until the grains are tender and the liquid is absorbed, about 10 minutes.

Place the squash in a large microwave-safe bowl with 2 tablespoons of water and cover tightly with plastic wrap. Microwave until the squash is very tender, about 15 minutes, then drain any excess liquid.

Heat the olive oil in a small skillet over medium heat. Sauté the onion until softened and translucent, then stir in the garlic, coriander, and five-spice powder and cook until fragrant.

Preheat the oven to 375°F and grease a 9-inch springform pan. Mash the cooked squash in a large bowl until smooth, or use a food processor for a finer texture.

Stir the soaked bulgur, sautéed onion mixture, flour, cilantro, mint, salt, and pepper into the squash puree. Mix thoroughly until the dough is uniform and holds together.

Transfer the mixture to the prepared springform pan and use a rubber spatula to smooth the top into an even layer. Bake until the kibbeh is firm and the edges have begun to pull away from the sides of the pan, about 35 to 40 minutes.

Sprinkle the feta and toasted pine nuts over the top. Let the kibbeh rest in the pan for 10 minutes before releasing the sides and slicing into wedges.