Marinate the Chicken: In a medium mixing bowl, combine all the marinade ingredients: Greek yoghurt, grated garlic and ginger, lemon juice, garam masala, turmeric, cumin, chilli powder, and salt. Add the chicken chunks and stir well to ensure every piece is thoroughly coated. Cover the bowl and place it in the fridge to marinate for at least 1 hour, or up to 8 hours for a deeper flavour.

Cook the Chicken: Heat 1 tbsp of the ghee or oil in a large, heavy-based frying pan or skillet over a medium-high heat. Once hot, lift the chicken pieces from the marinade, allowing any excess to drip off. Place them in the pan in a single layer (you may need to do this in two batches to avoid overcrowding). Cook for 3-4 minutes per side, until you get some lovely golden-brown, slightly charred spots. The chicken won't be cooked through at this stage. Remove from the pan and set aside on a plate.

Start the Sauce Base: Reduce the heat to medium and add the remaining 1 tbsp of ghee or oil to the same pan. Add the finely chopped onion and cook gently for 8-10 minutes, stirring occasionally, until soft, sweet, and translucent.

Add Aromatics and Spices: Add the grated garlic and ginger to the pan and cook for another minute until fragrant. Now, add the ground coriander, garam masala, smoked paprika, and chilli powder. Stir continuously for 60 seconds to cook out the raw spice taste.

Build the Sauce: Pour in the tinned chopped tomatoes, add the tomato purée and the teaspoon of sugar. Give everything a good stir, scraping up any browned bits from the bottom of the pan. Bring to a gentle simmer and let it cook for 10 minutes, uncovered, allowing the sauce to thicken and the flavours to meld.

Blend for a Smooth Texture: This is my secret to a restaurant-quality sauce. I find that using an immersion (stick) blender directly in the pan is the easiest way to get a velvety sauce. Carefully blend until smooth. If you don't have one, you can transfer the sauce to a regular blender, but be cautious with the hot liquid.

Finish the Dish: Return the seared chicken and any juices from the plate to the pan with the smooth sauce. Stir to combine, then pour in the double cream. Bring back to a gentle simmer and cook for a final 5-7 minutes, until the chicken is cooked through and the sauce has thickened slightly. Be careful not to let it boil rapidly once the cream is in.

Serve: Taste the sauce and adjust the salt if needed. Garnish generously with freshly chopped coriander and serve immediately.