Ingredients :

• Fresh yeast — Not baking powder, not dry yeast — fresh yeast, the little grey-beige cube found in the butter aisle. It gives a delicate aroma and a softness that dry yeast doesn’t quite match. If you can only find dry, use about 2.5 g of dry for 8 g of fresh, but dissolve it in warm milk anyway.
• The mix of type 0 / type 00 flour — This isn’t an Italian whim. Type 0 brings elasticity, type 00 brings finesse. Together, they create a dough that stretches without tearing. In many regions, a classic all-purpose flour works if you don’t have both — the difference is subtle.
• Butter — Use good butter, at least 82% fat. It’s what gives that round taste and melting texture. Margarine or low-fat butter would result in something much flatter, even a bit oily. This is not the place to save pennies.
• Unsweetened cocoa — Bitter, not sweetened — that’s important. Classic Van Houten works very well. It creates the visual contrast of the marble and brings the chocolate flavor without weighing down the dough. Sweetened cocoa powder would make the whole thing cloying.