In a mixer jar, add 30 g or ¼ cup garlic cloves and 2-inch ginger. Grind them coarsely. Then add a little water and grind into a smooth paste. Keep it aside.
In the mixer jar, add 250 g or 5 medium-sized roughly chopped onions. Add a little water and grind into a smooth paste. Keep it aside.
Now in a pan, add 3–4 cups of water and bring it to a boil. Make a cross cut on the top of each tomato. Add the tomatoes to the boiling water, along with 3 dry Kashmiri red chilies, and boil for 2–3 minutes. Switch off the gas, remove the tomato skins, and keep them aside.
Add the tomatoes and Kashmiri red chilies to the mixer jar, along with coriander stems. Add a little water and grind into a smooth paste. Keep it aside.
In a bowl, add ¼ cup cashews, ¼ cup watermelon seeds, and 1 tbsp poppy seeds. Add ½ cup hot water and soak for 20 minutes. When the cashews and watermelon seeds become soft, add them to the mixer jar with water and grind into a smooth paste. Keep it aside.
Take 1 cup oil; add ¾ cup oil into a pan. Add 1 tsp coriander seeds, 1 tsp cumin seeds, 5–6 cloves, 1-inch cinnamon stick, 2 bay leaves, 4 black cardamoms, 3 green cardamoms, 2 star anise, and 5–6 black peppercorns. Sauté them.
Then add the ginger-garlic paste and sauté until the oil releases from the sides.
Now add the onion paste and sauté on a low flame until the oil releases from the sides.
Lower the flame and add ½ tsp turmeric powder, 2 tbsp red chili powder, 2 tbsp coriander powder, 2 tbsp kitchen king masala, 1 tbsp sugar, and some hot water. Sauté the masala until the oil releases from the sides.
Then add the tomato paste and salt. Mix well, cover, and cook until the oil releases from the sides.
Now add the cashew–watermelon seed paste and sauté it. Add ½ cup hot water and stir continuously until the oil releases from the sides.
Add 2 tbsp kasuri methi to the gravy. Heat the remaining ¼ cup oil (from the 1 cup total) and pour the hot oil over the kasuri methi. Mix well. The addition of hot oil to the gravy gives it a perfect texture.
Add 1 tsp vinegar and 1 tbsp tomato sauce. Mix well, cover, and cook the gravy on low flame for 5 minutes.
The curry base is ready. Allow it to cool down and strain it.
Store the curry base in an airtight container. It stays good for up to 1 month in the refrigerator.