Allow the recipe registry to be modified.

src/main/java/net/minecraftforge/registries/GameData.java

@@ -128,7 +128,7 @@ public class GameData
         makeRegistry(SOUNDEVENTS,  SoundEvent.class,  MAX_SOUND_ID).create();
         makeRegistry(POTIONTYPES,  PotionType.class,  MAX_POTIONTYPE_ID, new ResourceLocation("water")).create();
         makeRegistry(ENCHANTMENTS, Enchantment.class, MAX_ENCHANTMENT_ID).create();
-        makeRegistry(RECIPES,      IRecipe.class,     MAX_RECIPE_ID).disableSaving().create();
+        makeRegistry(RECIPES,      IRecipe.class,     MAX_RECIPE_ID).disableSaving().allowModification().create();
         makeRegistry(PROFESSIONS,  VillagerProfession.class, MAX_PROFESSION_ID).create();
         entityRegistry = (ForgeRegistry<EntityEntry>)makeRegistry(ENTITIES, EntityEntry.class, MAX_ENTITY_ID).addCallback(EntityCallbacks.INSTANCE).create();
     }