Credit goes to @askan94 . I just reproduced and recorded.
Use a mottled gem in a shield which does damage while blocking. Start blocking, and while blocking, swap to a torch. The damage continues ticking even though you no longer have the shield equipped.
Easy shatter? I thought all those while blocking gems were elemental and you needed physical to shatter. Wouldn’t you also want to shatter with your biggest physical attack? I have a frost build where I use big one hit rune attacks on ice breaker and they slap. I’m not exactly sure what happens when you shatter, but it seemed to me like it doubles your attack damage, so you’d want to use a physical attack that slaps hard.