Prepare your ingredients: Peel, core, and dice the pineapple into small, roughly 1cm cubes. Finely chop the red onion and jalapeños, and mince or grate the garlic and ginger. Having everything ready before you start makes the process much smoother.

Toast the spices: Place a large, heavy-bottomed saucepan or Dutch oven over a medium heat. Add the mustard seeds and cumin seeds and toast for about 1 minute, or until they become fragrant and begin to pop. Be careful not to let them burn.

Sauté the aromatics: Add a splash of neutral oil (like rapeseed or sunflower) to the pan, followed by the chopped red onion. Sauté for 5-7 minutes until the onion has softened and become translucent. Then, add the minced garlic, grated ginger, and chopped jalapeños. Cook for another 2 minutes, stirring frequently.

Combine all ingredients: Add the diced pineapple, light brown sugar, apple cider vinegar, ground turmeric, and salt to the pan. If you're using them, add the red pepper flakes now. Stir everything together well to combine.

Bring to a simmer: Increase the heat and bring the mixture to a boil. Once boiling, reduce the heat to low and let it simmer gently, uncovered.

Simmer and reduce: Let the chutney simmer for 35-40 minutes, stirring occasionally to prevent it from sticking to the bottom of the pan. I find that stirring every 5-10 minutes works best. The chutney is ready when the liquid has reduced to a syrupy consistency and the mixture has thickened and looks glossy. The pineapple pieces should be tender and slightly translucent.

Cool and store: Remove the pan from the heat and let the chutney cool completely. As it cools, it will thicken further. Once cooled, transfer it to sterilised jars and seal.