Sienna is a small but perfectly formed restaurant that the casual glance might take to be one of the numerous tea shops on Dorchester's high street. But that would be well wide of the mark. With just 16 lucky diners to cater for, husband-and-wife-team Russell and Elena Brown can ensure a seriously refined, yet unpretentious gastronomic experience. Elena's domain is a simple, un-shouty dining room done out with solid ash tables and Mediterranean shades of ochre and terracotta, over which she presides with calm professionalism. At the stoves, Russell approaches his craft with a clear mind and finely-honed technical skills; there are no silly concepts or showboating, just honest cooking that gets everything right, delivering clear punchy flavours in well-thought-out combinations. Lunch menus offer storming value for food of this quality, but it is in the dinner and a tasting menu that things really take off. Poached fillet of brill with spring onion mash, prawns and saffron shows a feather-light touch, while main course could be a full-on truffle-crusted fillet of West Country beef with roasted sweetbreads, potato gnocchi and red wine jus. The invention continues at dessert: warm treacle tart could turn up in the company of spiced date purée, chestnut and apple salsa and vanilla ice cream.