Simple but impressive dinner party ideas for warm weather

[TFINaptime]

We have friends over on Saturday night, but I can't think what to cook. I want something simple, most of which can be done in advance. I think I just want a main and a dessert, but any simple starter ideas are always welcome.

Of course, it should go without saying that it all needs to make me look like a domestic goddess!

[OhBling]

How simple is simple? I do a really delicious thai beef salad which is lovely but might be a bit too casual for a dinner party?

Otherwise, I always think room temperature roasts are great in summer - lamb or chicken normally?