1 tablespoon vegetable oil
1 red onion, cut into wedges
5 cloves garlic, minced
1 tablespoon very finely minced fresh ginger
2 tablespoons curry powder, hot or mild
1⁄2 cinnamon stick
1⁄4 teaspoon ground cardamom (optional)
1 14-ounce can good-quality crushed tomatoes
Salt and pepper to taste
1 pound small red potatoes, unpeeled, cut bite-size
4–5 pounds chicken, cut into pieces, skin removed
1 cup Greek yogurt
1 cup fresh or defrosted frozen peas