Create an ultra-premium dessert advertising poster for a fictional patisserie "ÉCLAT BLANC". FORMAT: 4:5 vertical, minimalist elegant layout. SUBJECT: a delicate white chocolate éclair with a glossy mirror glaze, scattered pistachios and edible flowers, a clean knife-cut revealing pistachio cream filling. BACKGROUND: soft cream-to-pale-green gradient with gentle glow. LIGHTING: soft diffused light, glossy glaze highlights. TYPOGRAPHY: elegant serif logo "ÉCLAT BLANC" top-center, tiny tagline "Pure white elegance" bottom. FINISH: 8k, hyper-realistic food photography, refined finish.