Preheat your oven to 200°C (180°C fan or gas mark 6) and spread the peanuts evenly on a baking tray. Roast them for about 5 minutes until they turn a lovely golden brown and release their nutty aroma. Once cool enough to handle, roughly chop the peanuts to introduce delightful texture to the curry. Then, reduce the oven temperature to 180°C (160°C fan or gas mark 4) to prepare for slow cooking. In a large casserole dish with a lid, warm 2 tablespoons of coconut cream over medium heat. Stir in the massaman curry paste and gently fry it for 1 minute, letting the spices bloom and fill your kitchen with inviting scents. Next, add the strips of beef, stirring frequently to coat each piece thoroughly and seal in the juices, enhancing tenderness. Pour in the remaining coconut cream along with half a can of water to create a rich, flavorful sauce. Add the peeled and chopped potatoes, a wedge of thinly sliced onion, lime leaves, cinnamon stick, tamarind paste, sugar, fish sauce, and most of the roasted peanuts into the pot. Stir everything together before bringing the mixture to a gentle simmer. Cover the casserole with its lid and transfer it to the oven. Let it cook slowly for 2 hours to allow the beef to become incredibly tender and infused with all the deep, layered flavors. This slow cooking also softens the potatoes without losing their shape. Once finished, remove the dish from the oven and sprinkle the top with the remaining roasted peanuts and slices of red chili for a pop of color and mild heat. Serve the curry straight from the casserole alongside steaming jasmine rice to soak up the sumptuous sauce. Enjoy this comforting and aromatic dish that beautifully showcases traditional Thai flavors.