• Marinate the beef: In a large bowl, mix half the ginger, garlic, and Madras curry powder with a pinch of salt. Coat the beef cubes in the mixture and let it marinate for at least 1 hour (or ideally overnight) in the fridge.
• Heat the oil in a large heavy-based pan over medium heat. Add the mustard seeds, and when they begin to pop, add the curry leaves. Sauté for a minute.
• Add the chopped onions and cook for 10-12 minutes, stirring occasionally, until golden brown and softened.
• Stir in the remaining garlic, ginger, and sliced chillies. Cook for a couple of minutes until fragrant.
• Sprinkle in the ground cumin, coriander, turmeric, and chilli powder (if using). Stir well and cook for another minute to release the spices' aroma.
• Add the marinated beef cubes to the pan and brown on all sides, about 5 minutes.
• Pour in the chopped tomatoes and water (or beef stock), stirring to combine. Bring to a boil.
• Once boiling, reduce the heat to low, cover the pan, and simmer for 1.5-2 hours, stirring occasionally. Cook until the beef is tender and the sauce has thickened.
• In the last 10 minutes, stir in the garam masala and adjust the seasoning with salt to taste. Simmer uncovered if the sauce needs to reduce further.
• Garnish with fresh coriander leaves and serve hot.

Method (Ninja Foodi):

• Marinate the beef: As before, mix half of the ginger, garlic, and Madras curry powder with a pinch of salt. Coat the beef cubes in the mixture and marinate for at least 1 hour (or ideally overnight) in the fridge.
• Sauté the aromatics: Turn on the Ninja Foodi and select the 'Sauté' function. Add the vegetable oil to the pot. When the oil is hot, add the mustard seeds and let them pop, followed by the curry leaves.
• Cook the onions: Add the chopped onions and sauté for 6-8 minutes until softened and starting to turn golden.
• Add the garlic, ginger, and chillies: Stir in the remaining garlic, ginger, and sliced chillies, cooking for 2 minutes until fragrant.
• Add the spices: Sprinkle in the cumin, coriander, turmeric, and chilli powder (if using). Stir well and sauté for another minute to release the spices' aroma.
• Brown the beef: Add the marinated beef cubes to the pot and brown on all sides for about 4-5 minutes.
• Add tomatoes and stock: Pour in the chopped tomatoes and 200ml water or beef stock, stirring to combine. Bring the mixture to a simmer.
• Pressure cook: Cancel the 'Sauté' function, then seal the Ninja Foodi lid (with the pressure cooker lid, ensuring the valve is set to 'seal'). Select 'Pressure Cook' on high for 35 minutes.
• Natural release: Once the cooking time is complete, allow the pressure to release naturally for about 10 minutes, then carefully quick-release any remaining pressure.
• Finish with garam masala: Open the lid and stir in the garam masala. If the sauce is too thin, use the 'Sauté' function again to reduce it for 5-10 minutes, until thickened to your preference.
• Serve: Garnish with fresh coriander leaves and serve hot with rice or naan.

Hot Tips (for Ninja Foodi cooking):

• Make sure the beef is cut into evenly sized pieces to ensure even cooking under pressure.
• If you prefer a more tender texture, you can add an additional 5-10 minutes to the pressure cooking time.
• Reducing the sauce after pressure cooking helps concentrate the flavours if it’s a bit watery.