This was something that really caught me by surprise when I started playing very recently. I’ve struggled with the same thing with my Yamaha Ecodear, which leads me to having to practice clearing it. So far my favorite method of clearing it is to put a finger over the top of the fipple, but still leaving the bottom open, which prevents it from making any noise, but lets me blow really hard. I don’t know how the more experienced players here feel about that, but it seems to work, and I prefer it over sucking the spit back in. 🙂
I’ve been considering putting my recorder under an electric heating pad for a bit before playing it, though I’d want some kind of temp control so that I don’t over-heat it.