Symfony 6.1 - How to run a background task for inserting entries into the database?

I am currently working on a Symfony 6.1 project and have a database insert that needs to generate quite a lot of entries (30k+). I would like to run this insert process as a background task and once all entries have been created in the database, I would like to send an email.

Now I found the following article about Background Task in the Symfony documentation: https://symfony.com/doc/current/components/process.html#running-processes-asynchronously

However, I don't quite understand how to get the process to run in background.

My current code:

        $process = new Process(); //not sure what to put in for the constructor
        $process->start(function ($data) {
            foreach($data as $key => $value) {
                $value->setExampleValue("example");
                $this->entityManager->persist($value);
                $this->entityManager->flush();
            }
            ... email code
        });

        if (!$process->isSuccessful()) {
            throw new ProcessFailedException($process);
        }

UPDATE:
As someone noticed I have had a look on the Commands from Symfony. Now I tried to start my custom Command as a Process. However each time I start the Command it fails and the Exit Code is: (). This is the code:

        $process = new Process(['php bin\console app:generate-test']); 
        //$process->setWorkingDirectory(substr(getcwd(), 0, strrpos(getcwd(), '/')));
$process->start();
    

        if (!$process->isSuccessful()) {
            throw new ProcessFailedException($process);
        }

However, if I start the command via the console "php bin/console app:generate-test" it works and I get a simple textline printed in my console window.

Has anyone an idea what I am doing wrong here?

FINAL SOLUTION:

Instead of the Process Component from Symfony I switched to the Messenger Component as recommended in the comments.

This works now like a charm!

I found a great tutorial series for understanding and implementing the messenger: https://www.youtube.com/watch?v=Xwn_BNfyjgk

I think you should look at commands (https://symfony.com/doc/current/console.html)

You can then run the command and minimize the console window or use a process manager (like Supervisor) to run it in the background.