Risotto di Zucca, Porri, e Vongole (Risotto with Butternut Squash, Leeks, and Clams)

Ingredients

• ¹⁄₂ lb. butternut squash, peeled, seeds and strings removed, and squash cut into dice no larger than 1/2"
• 18 live littleneck clams, scrubbed
• ¹⁄₄ cup extra-virgin olive oil
• 1 large or 2 medium leeks, trimmed, washed, halved lengthwise, then cut crosswise into very thin slices
• 2 tbsp. scallions, white part only, cut into very thin rounds
• Fine sea salt
• 1 tbsp. chopped fresh marjoram, or 1/2 tbsp. dried marjoram
• 1 cup Italian risotto rice, such as carnaroli, vialone, nano, baldo, or arborio
• 1 cup dry white wine
• 1 tbsp. whole green peppercorns
• ¹⁄₂ cup grated pecorino cheese