If I understand things correctly, you have to have logged in with the specified user name at least once while online in order to play in "offline mode" with it.

You will also need to be online at least once in order to download the actual game (the launcher does not contain any game binaries, just the code needed to verify your login and start up the game).

If you copy the .minecraft folder from a computer which you have logged into MineCraft before, you might be able to just copy over the config files to the "offline" computer.

EDIT: After some testing by the asker, it seems this is not how MineCraft works any more with the new launcher.

If I understand things correctly, you have to have logged in with the specified user name at least once while online in order to play in "offline mode" with it.

You will also need to be online at least once in order to download the actual game (the launcher does not contain any game binaries, just the code needed to verify your login and start up the game).

If you copy the .minecraft folder from a computer which you have logged into MineCraft before, you might be able to just copy over the config files to the "offline" computer.