How would I use an event to spawn a mob?

here is the code I have so far. I am trying to make a spawn egg.

 @SubscribeEvent
    public static void onClickEgg(PlayerInteractEvent event) {
        if (event.getEntityLiving().getHeldItemMainhand().getItem() == ModItems.SPAWN_MUDDY_PIG.get()) {
            PlayerEntity player = event.getPlayer();
            
        }
    }