What is this white stuff?

That’s just some soil fungus that’s forming. Likely the soil is taking a long time to dry out. Nothing to worry about. Just get a fork or a small hand rake and break up the surface of the a soil a little bit and it will disappear. Breaking up the surface of the soil will also help when you go to water next time. If you leave it as it is once it’s dry the water won’t want to penetrate that top caked up layer. No sress, no seeds, no sticks.