Combine all spice paste ingredients in a bowl with 3 tablespoons of water to form a paste.
In a medium sized pot, heat vegetable oil. Fry cinnamon stick, cardamom pods, and cloves for 1 to 2 minutes or until spices start to pop.
Add onion, garlic, and ginger and fry for another 2 minutes.
Then add spice paste and continue to cook for 4 to 5 minutes over medium heat. Stir constantly so that the spices do not burn.
Now, add chicken and continue to cook for another 4 to 5 minutes.
Pour in ½ cup (120ml) water, cover, and bring to a boil. Reduce heat and allow it to simmer for 10 minutes.
Season with salt to taste. Add potatoes and continue to cook for 10 minutes.
Finally, add tomatoes and stir in yogurt. Allow it to simmer for about 3 minutes.
Turn off heat and let korma sit for 10 minutes.
Sprinkle roasted cashew nuts on the top and served with steamed basmati rice.