First, cut the chicken thighs into halves or thirds, depending on their size. Place them into a bowl and add all the marinade ingredients: yoghurt, Kashmiri chilli powder, ground coriander, ground cumin, ground turmeric, and a sprinkle of salt. Stir well to coat the chicken evenly, ensuring that each piece is enveloped in the spices. Cover the bowl and refrigerate overnight to allow the flavors to meld.
When ready to cook, remove the marinated chicken from the fridge and let it sit at room temperature for about an hour. This helps the chicken to cook evenly.
Meanwhile, prepare the spinach. Blanch the washed leaves in a large pot of salted boiling water for about three minutes. Once bright green and tender, drain them in a colander and rinse under cold water to stop the cooking process. This keeps the vibrant color intact. After cooling, puree the spinach in a blender until smooth. If necessary, add a little water to help it blend.
Preheat your oven to 200°C (about 392°F). Line a baking tray with tin foil and lightly spray it with cooking spray. Spread the marinated chicken pieces evenly on the tray, ensuring they are not overcrowded. Roast in the preheated oven for thirty minutes.
After fifteen minutes, remove the tray and drain any released liquid from the pan. Turn the chicken pieces over, then brush them with melted butter. Return the tray to the oven and continue roasting for the remaining fifteen minutes or until the chicken is lightly golden and succulent.
While the chicken is roasting, prepare the sauce. In a food processor, blend the onions and garlic until finely puréed but still slightly textured. Heat a large nonstick frying pan or skillet over high heat and add the vegetable oil. Once hot, sauté the onion and garlic mixture for about eight to ten minutes, stirring regularly until it starts to brown.
Add the puréed tomatoes to the food processor and blend until smooth, then incorporate this into the pan once the onions are browned. Stir to combine.
Now, add the chopped chilli, grated ginger, ground coriander, ground cumin, Kashmiri chilli powder, ground turmeric, and garam masala. Cook for a minute or two until fragrant, stirring frequently to release the spices' aromas.
Introduce the puréed spinach to the pan and let the sauce simmer for an additional six to eight minutes. Taste and add more salt as necessary to balance all the flavors. After a few minutes, stir in the yoghurt and fresh lemon juice, melding the ingredients into a creamy sauce.
Finally, add the roasted chicken to the simmering curry sauce. Gently toss to ensure each piece is covered in the rich sauce. Heat through, checking the seasoning once more to ensure it has the perfect balance.
Serve your Saagwala hot, ideally accompanied by fluffy basmati rice or warm naan bread to soak up that delicious sauce.
