Roasted Kabocha Squash Soup with Ginger Butter

Ingredients

• Vegetable oil
• 1 kambocha or other Winter squash, about 3 ½ pounds
• 1 tablespoon butter
• 1 tablespoon olive oil
• 2 leeks, white and light green parts only, cleaned and roughly chopped
• 1 thick (about ¼ inch) slice Prosciutto di Parma, cut into ¼-inch cubes
• 5 cups vegetable broth
• 1 ½ cans (2 ¼ cups) coconut milk
• ¾ teaspoons ground cardamom
• ¾ teaspoons ground coriander seed
• 2 oranges
• 3 tablespoons butter, at room temperature