netcat in a batch file to run it as a separate process

I want to run netcat as a separate process inside a batch file. For that purpose I am using the following method

start "" netcat.exe -l -p 1234 > output.txt

however with this option, the output.txt is showing zero bytes. I guess it is considering it as output of start rather than of netcat.

If I use the following way, it works fine but I want to run parallely in the batch file so that I can proceed with other things in the batch file

netcat.exe -l -p 1234 > output.txt

Please suggest me how can I achieve this..