Step 1: Prepare Ingredients

Finely chop the red onions and tomatoes. Peel the garlic and roughly chop the ginger. Soak the cashew nuts in water for at least 2 hours, then drain.

Step 2: Temper Spices and Sauté Aromatics

Heat 200ml of oil in a large karahi or heavy-bottomed pan over medium-high heat. Add the whole spices (bay leaves, cinnamon, green and black cardamom, peppercorns, cloves, star anise) and temper for about 30 seconds. Add the fresh garlic and ginger and fry until the garlic begins to turn brown.

Step 3: Cook the Onions

Add the finely chopped red onions and 1 tbsp of salt. Stir well to coat everything in oil. Cover the pan, reduce the heat to low, and let the onions soften for 10-12 minutes, stirring occasionally.

Step 4: Cook Tomatoes and Nuts

Remove the larger whole spices (bay leaves, cinnamon sticks, black cardamom, star anise). Add the green chillies, soaked cashew nuts, and chopped tomatoes. Stir, cover the pan again, and cook on low heat for another 20 minutes until everything is very soft and mulched down.

Step 5: Cool and Blend

Turn off the heat and let the mixture cool down completely. Once cool, transfer it to a high-powered blender and blend until it forms a very smooth paste, adding a little water if necessary to help it blend.

Step 6: Cook the Spices

In a clean pan, heat the remaining 200ml of oil and 2 tbsp of ghee. In a separate bowl, mix all the powdered spices (cumin, coriander, turmeric, Kashmiri chilli, garam masala) with a little water to form a paste. Add this spice paste to the hot oil and cook for 1 minute, stirring constantly.

Step 7: Final Simmer

Pour the blended base paste into the pan with the cooked spices. Stir everything together thoroughly. Add the brown sugar and stir it in. Put the lid on, turn the heat to low, and let it simmer for a final 20 minutes. The base is ready when the oil has separated and risen to the top.

• Use red onions, not white or Dutch onions, for the best result and authentic flavor.

• If you have a nut allergy, you can substitute cashew nuts with mung dal for creaminess.

• You can skim off the excess oil after cooking and use it as a spiced oil for other curries.

• To cool the mixture quickly before blending, place a clean bag of ice packs in the center of the pan.

• The finished base can be stored in the fridge for up to 10 days or frozen for later use.

• Use this base to make a variety of Indian restaurant-style curries, such as Madras.