buttery veneziana

I'm more and more convinced that flour was born to be used as butter carrier!
The formula for this bread is very simple:
100% bread flour (13% proteins) (300 gr)
83% whole eggs (250 gr)
40% sugar (120 gr, something more wouldn't hurt)
28% firm starter (80 gr)
83% butter (250 gr)
3% milk powder (9 gr)
2% salt (6 gr)
flavors (I used 10 gr of Marsala liquor). Orange zest and vanilla are very good candidates. Flavors are essential.