Clash with Ash Hard mode
I've been having trouble with this specific stage for 2 days now and after some mix and match I've found the perfect duo.
Venom dough cookie and wind archer cookie.
Some of you might have problems surviving the initial attack (I know, cause I did also lol) don't worry this is still full auto gameplay, but after you start when the cookies are near the little stairs in front of ash before the sign "boss battle" pops up click on Pure Vanilla's skill already and toggle Hollyberry's skill so that when you enter the battle your cookies will already have a shield and Hollyberry will instantly cast her skill. That's how I survived the initial attack.
As you can see my ancients aren't even at level 100, the only max level there is wind archer cookie. Venom dough is max level but her skill is lvl 53. IDK if having lvl 18 crystal jam plays a BIG part because if I remember correctly I still had about more or less 50 seconds left on my timer.
I know this might not help everyone, but to those willing to try tell me if it worked for you also.
Edit: at the end are the treasures I used.