Heat the oil in a medium saucepan or Dutch oven over medium heat.
Add the diced onion, minced chile, turmeric, coriander, cardamom, garlic, ginger, and the cinnamon stick.
Sauté for 2-3 minutes, stirring constantly, until the spices are fragrant and the onion has softened.
Add the raw cashews, diced potatoes, coconut milk, and salt to the saucepan.
Stir everything together and bring the mixture to a gentle boil.
Reduce the heat to low, partially cover with a lid, and let the curry simmer for 20-25 minutes.
Stir occasionally to prevent sticking. The curry is ready when the potatoes are fork-tender and the sauce has thickened to a creamy consistency.
Remove the cinnamon stick before serving.
Taste and adjust salt if needed.
Serve hot on its own or with steamed basmati rice and fresh cilantro.
Stir in a few handfuls of fresh spinach during the last 5 minutes of cooking for added nutrients and a vibrant pop of color.