1 large leek, white and tender green parts only, halved lengthwise

1/4 cup olive oil, divided

1 lb. butternut or acorn squash, peeled and cut into 1-inch dice

1 medium-sized onion, chopped

1/4 teaspoon saffron threads

1/4 teaspoon cayenne pepper

2 cups Valencia or Basmati rice (or regular long-grain rice)

2 cups low-sodium chicken stock

1 1/4 cups dry white wine

One 14 ounce can whole tomatoes, drained and chopped

One 14 ounce can quartered artichoke hearts (in water), drained