craftingTable.removeRecipe(<item:projecte:philosophers_stone>);
craftingTable.addShaped("philosophers_stone", <projecte:philosophers_stone>,
 [[item:minecraft:redstone>, <item:minecraft:ghast_tear>, <item:minecraft:redstone>],
  [<item:minecraft:ghast_tear>, <item:minecraft:diamond>, <item:minecraft:ghast_tear>],
  [<item:minecraft:redstone>, <item:minecraft:ghast_tear>, <item:minecraft:redstone>]], null);