Great video, thank you for doing them for us! Can I use pastry flour as substitution?

Yes, absolutely. I've found that pastry flour always works as a substitute for all purpose flour in any baked recipe other than yeast breads.

Pasty flour is simply a lower protein / lower gluten flour. That makes it a poor choice for breads where you want stretch and strength, but makes it a good choice for cakes like this, where you want a tender crumb. ;o)