Whether you buy ready made pastry cases, or spend a little time cutting out little circles of puff pastry, brushing them with butter and baking them in a muffin tin (easy peasy), you're left with a hardy vessel ready to be filled with all manner of things that can be made ahead of time:
simple prawn cocktail, easy guacamole, maybe topped with a little bacon and sour cream, goat's cheese with tomato salsa and basil... all these are easy and quick.