I'm probably an idiot

    @Override
    public ActionResult<ItemStack> onItemRightClick(World worldIn, EntityPlayer playerIn, EnumHand handIn)
    {
        if(playerIn.inventory.hasItemStack(new ItemStack(this)))
        {
            int invSize = playerIn.inventory.getSizeInventory();
            for(int i=0; i<invSize; i++)
            {
                if(playerIn.inventory.getStackInSlot(i).getItem() == Items.IRON_INGOT)
                {
                    ItemStack IronIngotFound = playerIn.inventory.getStackInSlot(i);

                    IronIngotFound.stackSize--;
                }
            }
        }
        return super.onItemRightClick(worldIn, playerIn, handIn);
    }