When a sturdy jug of water and a delicate bag of flour love each other very much, what will emerge from their union? A baby made of bread-dough, obviously. It sounds a ludicrous premise for a show, but puppeteer Helen Ainsworth turns the jocular set-up into a telling parable for our times –tackling a series of important contemporary issues, with plenty of physical humour yet with emotional sensitivity, too.

Ainsworth presides over proceedings with an air of awe-struck reverence, somewhere between a proud godparent and an artisan cook. But it's the characters she conjures on her kitchen-style worksurface who are the real stars of her show: they're made from the sparsest of ingredients, yet they're oh-so familiar. Father Keith (a well-built water jug) is kind-hearted but tongue-tied, while mother Beryl (who's literally just a bag of flour) is emotional, self-centred, and prone to elaborate swoons.

Janet, the title character, is Keith and Beryl's baby – and yes, she really is a "puppet" made from a lump of uncooked bread-dough. The malleable dough is a neat metaphor, capturing a sense of the unformed potential present in every child, and the messy unpredictability of the material adds an extra dimension of humour. But Janet, despite her shapeless form, is thoroughly believable, and Ainsworth's excellent vocal work also helps build characters I came to perceive as living and real.

Just as realistic are Janet's childhood troubles, which partly reflect everyday growing pains and partly serve as a piquant comment on the pressures of society. Keith's emotionally repressed – as all thickset metal jugs surely are – yet he's the one who tells Janet she's beautiful, while her mum plants seeds of doubt that she'll ever measure up. And lurking in the background is Lady Grey, a teapot with shades of Lady Chatterley, who's fallen for the unrefined Keith and is plotting to prise the family apart.

There are big topics in play here: themes of body-shaming, self-realisation, and the harm both societal pressure and parental ambition can cause in formative years. Towards the end things get genuinely dark, as the emotionally-damaged Janet enters her inevitable teenage rebellion. But there's also a lot of irreverent humour to enjoy, including several hilarious instances of out-and-out doughy innuendo.

Occasionally scenes dragged and, even though Janet clocks in at just 45 minutes, I'm not convinced there's quite enough in the concept to sustain a whole show. But it earns the fourth star for the sheer chutzpah of it all: its bizarre but successful melding of dough-based physical comedy and insightful social commentary. However many years you've been coming to the Fringe, you've never quite seen it all. Make sure you see this one.