Clean the offal thoroughlyRinse liver and spleen with water and a squeeze of lime or vinegar to remove any strong odor. Boil briefly and drain. Boil the beef and offal separately until tender. Remove and cut into bite-sized cubes. Reserve 500 ml of the beef stock for the broth.
In a large pot, heat oil and sauté the spice paste together with bay leaves and lemongrass over medium heat until fragrant and the paste turns a bit oily (about 5–7 minutes).
Add the cooked beef and offal pieces. Stir well to coat them evenly with the spices.
Pour in the beef stock and thin coconut milk. Bring to a gentle simmer over medium heat. Let it cook uncovered until the broth reduces by about half.
Lower the heat and stir in the thick coconut milk. Simmer gently (do not boil) until the curry thickens and oil begins to surface on top.
Taste and adjust seasoning with more salt or bouillon if desired.
Serve hot, topped with sliced scallion and crispy fried shallots.