Combine 4 cups of water with ginger, scallions, and smashed garlic in a medium stockpot. Bring to a boil over medium-high heat. Add the clams, and reduce heat to medium. Remove the clams with a slotted spoon when the shells begin to open. Once all the clams are removed, simmer the remaining stock for 10 minutes. Remove from heat, strain, discarding the aromatics. Set aside the stock.
Heat 2 tablespoon butter and 1 tablespoon oil in a medium pot over medium heat. Add the chopped onion, garlic and ginger, cooking until the onions are translucent, about 4-5 minutes. Add the flour and curry powder, stirring to make a paste. Add the tomato paste, potatoes, carrots, bay leaf, grated apple, and 3 cups clam stock. Cover and bring to a boil. Reduce heat to medium-low and simmer for 15 minutes or until the vegetables are cooked.
While the curry is cooking, remove the clam meat from the shells, discarding the shells. You can also keep some of the clams in the shell for presentation.
Season curry with soy sauce, honey, salt, and pepper. Add back the clams, stirring to combine. Serve with steamed rice.