Southrop, Lechlade, Gloucestershire (01367 850 205). Meal for two, including wine and service, £110

I went to the Swan at Southrop following the luscious promise of one item on the online menu. From this I can firmly say: never invest all your dining happiness in a single plate of food. No good can come from it. Mind you, that one dish did sound like a corker. It was a whole vacherin cheese, baked in the oven and served – for two – with roasted garlic and Melba toast. There is a part of me – the ornery, sneering, eye-rolling part – which is suspicious of those who bang on about the joys of seasonal dishes, not because seasonality is a bad thing – it can be marvellous – but because when people start hollering about how much they love it, they seem to be telling you less about the food and so much more about themselves: how authentic they are, how they do so cleave to the nourishing rutted earth, how deeply they like to suckle at Mother Nature's teat.

And so on. That said, the vacherin Mont d'Or really is one of those truly marvellous seasonal foods, a cow's-milk cheese with a wobbly orange-ish rind, generally available between September and May, which has to be sold in a round wooden box because, in its perfect ripe state, it is so runny it will make a dash for the door. Put a bit of foil round the base, pour on half a glass of wine, shove it in the oven and, hurrah, you have an instant fondue, albeit one with a serious kick. The Swan at Southrop advertised one of those on its menu. Ergo I had to eat there.

So off we went. It is a solid old Cotswold pub with fires in the grate, pork scratchings at the bar and a wide-ranging, eccentric menu of dishes from all over. There is a cookery school on site, and one can't help wondering if the menu, with its references to Oriental vegetables, teriyaki of salmon, tempura and dishes lifted from Morocco, Italy and France, is regarded as a shop window for what they can teach. It has a restless, unfocused feel. What it didn't have was a vacherin. All gone. None for you, I'm afraid. Instead they were doing a camembert. I should have embraced the disappointment. I should have accepted their pained regrets and chosen something else – the potted pheasant, perhaps, or the ribollita – but I had my cheese head on. It was what I had come for, and I was a little too determined. Along came a small round of dry, wineless camembert, which hadn't been baked for long enough, with half a bulb of roasted garlic. Quickly it solidified on its board. A huge disappointment and, being for two, a waste of other ordering opportunities.

A thing like that can colour a meal, so let me try to be objective. Service here is lovely and unflustered, there's an interesting wine list, and on a quiet weekday the old stone-walled rooms have a pleasing, affable hum. You could imagine hunkering down here until daylight leaked from the sky. The cooking, however, is a little patchy: not in that "What were they thinking?" way. It is more about precision, as if certain dishes have slipped out of focus. A lamb knuckle tagine with merguez, chicken and chickpeas, for example, was a well-cooked, long-braised assembly, but it was a little well mannered, an expression of the Cotswolds on a plate. It needed a serious kick of harissa rather than the limp dollop of what tasted like a harissa-flavoured mayo. Much better was calf's liver with a horseradish crumb, crisp pancetta, and bubble and squeak dressed with brown butter. It was the latter that dominated, in a good way. This was a victory for hot butter, a hymn to frying stuff off in dairy fats.

A fruit crumble with a disappointingly dusty, nutty topping was saved by more dairy fats – lots of pouring cream – and we especially liked the salt caramel ice cream that came with an apple tarte fine. Sadly, the tarte itself was undercooked, the fruit breaking on the spoon rather than slipping apart. The latter makes this sound like a less-than-whelming meal, and at over a ton for two, it is very hard to claim otherwise. It was nice – the Swan is not a bad place – but is nice enough? In an increasingly crowded country pub market, a certain blanding out seems to be spreading. Granted, it's all so much better than it was even five, let alone 10 years ago. But distinctiveness, originality, a clear culinary voice is harder and harder to find these days. It's a shame. Sometimes it really is better to travel hopefully than to arrive.

Email Jay at jay.rayner@observer.co.uk or visit theguardian.com/profile/jayrayner for all his reviews in one place