One of the best recipes I've found for a dinner party is the Chocolate Souffle below. It's easy to make (my criteria!) and can be made ahead.
Chocolate Souffle (for 6)
200 grams dark chocolate (70 per cent cocoa is best)
150 grams butter, cubed
175 grams caster sugar
125 grams plain flour
Double cream or ice cream to serve
Heat the oven at 180 degrees Celcius, if cooking right away. Butter 6 ramekins well. Melt the chocolate with the butter in a bowl over simmering water, or in a microwave.
Beat the eggs with the sugar until very light and fluffy. Then fold in the flour. Fold in the chocolate mixture and divide among the ramekins.
Put it in the fridge at this point, if you are making ahead or bake it for 8-12 minutes.
The souffle should rise and form a firm crust, but still runny on the inside. Serve with some double cream or a scoop of vanilla ice cream.