Design a playful, retro-inspired poster featuring a stylized Bellini cocktail, rendered in soft pastel colors. Use simple, hand-drawn lines to capture the essence of the Bellini's elegance, with subtle elements like peach slices and bubbles to evoke its refreshing taste. The background should be minimal, allowing the Bellini to be the centerpiece, all while maintaining a sweet, nostalgic feel. Aim for a composition that is both simple and inviting, perfectly encapsulating the joy of a leisurely sip of this classic cocktail.