Put the bread flour, cake flour and salt in a bowl. Add the boiling water and mix well with a wooden spatula.
When the dough is firm enough that it can be collected for a ball and is cooled down enough to touch, knead it well (be careful not to burn yourself.)
When the dough is about as firm as your earlobe, wrap it in plastic wrap and let rest for 20 to 30 minutes.
Roll out very thinly with a rolling pin. You can make 8 15 x 15 cm square spring roll wrappers, or 30 10 cm diameter gyoza skins from this dough.
A bit uneven, but this is a gyoza skin. Rotate the skin as you roll it out to make it round.
Story Behind this Recipe
I think this homemade skin/wrapper is more bouncy and chewy than storebought. It's fun to make with the kids, you can make memories as well as delicious things together. If it's difficult or just a bother to roll the the gyoza skins out so they're round, you can roll out the dough in a large piece and cut it out with a cookie cutter or something similar (like the lid of a container). I've never done it that way myself, but I've seen it done on TV in that fashion.
The key is to keep rolling out the dough until you think you can't possibly roll it thinner.