Lamb Tagine with Prunes

Ingredients

• * 3 pounds lamb shanks, sawed into 1-inch pieces
• * 3 medium onions, peeled and grated, two peeled and thickly sliced
• * 1 tablespoon ras el hanout, plus more to taste*
• * Salt and freshly ground black pepper
• * 1 tablespoon plus 1 teaspoon unsalted butter
• * Large pinch saffron
• * 1 cinnamon stick
• * 1 teaspoon olive oil
• * 2 teaspoons sugar
• * 1/2 cup canned crushed tomatoes
• * 1 cup canned chickpeas
• * 3 cups pumpkin or butternut squash chunks
• * 3/4 cup pitted prunes, halved