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
1/2 lb. Swiss chard, stems discarded, coarsely chopped