To peel the pumpkin, halve it, and then scoop out the seeds. Cut it into wedges, carve the flesh away from the skin, and then chop it into 1-inch cubes. (If using butternut squash, cut the squash in half, separating the upper half from the bulbous bottom. Use a sharp vegetable peeler or paring knife to trim away the skin. Chop the squash into 1-inch cubes.) Place the pumpkin on a baking sheet and drizzle with 2 tablespoons EVOO and season with the salt, pepper and nutmeg. Place in the oven and roast until golden brown and cooked through, 30 to 35 minutes. Add the pistachios during the last 5 to 10 minutes of cooking. Let cool to room temperature.
While the pumpkin is roasting, make the vinaigrette. In a small mixing bowl, combine the vinegar, honey and mustard. In a slow stream, whisk in the remaining EVOO, add the chives and season with salt and pepper.
In a large mixing bowl, combine the cooked and cooled pumpkin with the pistachios and the baby spinach and arugula. Toss and the adjust seasoning. Arrange on a platter and top with crumbles of the gorgonzola.