Ingredients :

• White chocolate — This is what gives the blondie its characteristic color and sweetness. Use baking white chocolate or a classic bar with at least 30% cocoa butter—budget brands melt poorly and can become grainy at the slightest heat. It melts much faster than dark chocolate, so stay at a gentle simmer over a bain-marie and stir regularly.
• Kinder Maxi bars — Cut them into large chunks, not small pieces. If they’re too small, they disappear completely into the mass. In large pieces, they create pockets of milky chocolate that you find when biting in. Three bars for an 18 cm mold is the right amount—present enough without unbalancing the batter.
• Chocolate spread — Nutella, homemade hazelnut spread, or any version you love. It sits between the two layers of batter and stays partially melted even after baking. Drop it in small dollops rather than a thick layer—if it’s too concentrated in one spot, the center won’t bake correctly.
• Butter — Unsalted butter, not semi-salted. It melts with the white chocolate and forms the entire fatty base of the batter. Don’t use margarine here—the final texture will be different, drier, with less structure when slicing.