Sourdough Bomboloni

Fried these up this morning for a friend's birthday and I am so happy with them! I am pretty novice at sourdough, but had been eyeing this recipe for a long time and so glad I tried it.
The recipe is TPL Sourdough Bomboloni, and I doubled all his quantities, which made exactly 36 doughnuts. https://www.theperfectloaf.com/naturally-leavened-bomboloni-doughnuts/

506g All-Purpose White Flour
506g High Protein Bread Flour
374g Eggs (7 eggs)
202g Unsalted Butter
202g Fine White Sugar
182g Water
20g Salt
406g Mature 100% hydration levain

Built levain in the morning, started to mix around 4pm

-Put everything but the butter in the stand mixer, mix on speed 2 for 5 min, rest for 10.
-Mix on speed 3 for 10 min, adding slightly soft butter a chunk at a time.
-Dough was almost to full windowpane at end of mixing.

-Bulk proof for 6hrs @80ºf (recipe said 78⁰, I did 80⁰ in hopes of going to bed earlier, but I still gave it the full 6 hours – I suspect my levain wasn't quite as active as it could've been)
-Did 4 sets of stretch & folds @ 30min intervals from start time.
-Cold bulk overnight.
-Divide and shape into 65g rounds (I did this around 1pm), with very taut surfaces.
-Proof for another 12hrs (I did this in two phases with another fridge overnight so I could fry them in the morning)
After shaping I made the filling – pastry cream recipe included in the link above turned out delish.

-Fry in refined coconut oil @370⁰f, ~2min per side
-Dust in cinnamon sugar, pipe in the pastry cream, and voila!

They were a total hit. The dough is not overly sweet at all (that's where the cream comes in), and the texture was great. I feel like mine turned out a bit more dense than they could have if my starter was stronger – it had been in the fridge a few days and could've had longer to wake back up. That said, the doughnuts were still light and airy, and I'll definitely be making them again 😁