Prepare the beef. Cut the beef into approximately 1.5-inch cubes (4x4 cm). Set aside.
Make the base sauce. In a large heavy-bottom pot or Dutch oven, mix the coconut milk, blended spice paste, kaffir lime leaves, lemongrass, turmeric leaf (if using), and tamarind. Bring to a boil over medium heat, stirring occasionally.
Add the toasted coconut. Add the ground toasted coconut (or toasted desiccated coconut paste) into the simmering sauce. Stir well to incorporate.
Cook the beef. Add the beef into the pot. Lower the heat and simmer uncovered for 2.5–3 hours, stirring occasionally to prevent burning. Cook until the sauce thickens, the beef is tender, and the oil begins to separate. The color should darken to a deep brown.
Finish and serve. When the sauce is fully reduced and clings to the beef, and the meat is fork-tender, turn off the heat. Serve hot with steamed rice.