Step 1: Combine Vegetables

Place the peeled and roughly chopped onions, garlic, ginger, white cabbage, carrot, and red bell pepper into a large pot.

Step 2: Add Water and Salt

Add enough water to just cover the vegetables in the pot. Stir in 1/2 tablespoon of salt.

Step 3: Boil and Simmer

Bring the mixture to a boil, then cover with a lid and let it simmer for about 30 minutes, or until all the vegetables are soft.

Step 4: First Blend

Once the vegetables are soft, turn off the heat. Using an immersion blender, carefully blend the mixture until it is very smooth. This may take 3-5 minutes.

Step 5: Add Remaining Ingredients

Add the tin of chopped tomatoes, 3 tablespoons of mild Madras curry powder, and the handful of fresh coriander to the blended mixture.

Step 6: Second Blend

Blend everything again until completely smooth and all the new ingredients are fully incorporated.

Step 7: Final Cook

Turn the heat back on and bring the gravy back to a simmer. Cook for a final 10 minutes, stirring occasionally to prevent it from sticking.

Step 8: Final Blitz and Finish

Give the gravy one last blitz with the blender to ensure it's perfectly smooth. The base gravy is now ready to be used or stored.

Step 9: Prepare for Use

To use the gravy for cooking a curry, thin it down with water until it reaches the consistency of semi-skimmed milk. The rest can be cooled, portioned into 300ml bags, and frozen for future use.

• This base gravy can be portioned out (e.g., 300ml bags) and frozen for later use.

• When ready to cook a curry, thin the base gravy with water to the consistency of semi-skimmed milk. This helps the spices cook out and caramelize properly.

• Blend the gravy for a long time (3-5 minutes) to get it really smooth.

• For safety, let the mixture cool down before blending to avoid accidents with hot liquid.

• You can use a pre-made Indian restaurant 'mix powder' instead of mild Madras curry powder.