Loading Screen for Procedurally Generated Map

I thought using Async would be too easy. Yup, twas. It loads the empty scene, says "progress complete!", and then starts the map generation, which is what actually takes up the time, so the player is staring at a frozen screen for about 15 seconds. No music, no nothing.

What I don't get, however, is why is it stuck on the title screen, even during the procedural generation? It seems to me it would load the scene without the generated map first, and then lock up as it generates the map.

How do I tell it to load the map generator scene, then generate the map, so I can have the map generator script itself feed information to a loading bar?