The best-looking construction site in Sydney has to be the new Gelato Messina Dessert Bar in Darlinghurst. Lit up by neon glitz and filled with multi-colour rows of ‘assembly parts’ (fudges, jellies, sweets galore) and carnival-style equipment (a fairy-floss machine, a popcorn incubator), this build-your-own sundae establishment is a sugar-fuelled delight. In fact, it’s basically a funhouse of decision-making – the set-up is like filling out a Census form, except all the questions are about what you crave in a dessert.

You start by picking a base (cup, plain or raspberry waffle cone, crepe, choux puff or donut), adding your own soft-serve gelato, (the current selections are burnt vanilla, Fanta sorbet, or a mash-up of both) for a total of $7.50, and then you can go all out with additions and toppings (80c each), which include hot fudges (smoked chocolate/white chocolate and hazelnut/butterscotch), choc top dip (chocolate/caramel), foams (mango/coconut), jellies (raspberry/strawberries and cream), gels (mandarin/raspberry), ‘creamies’ (redskin custard, burnt honey mousse/Cointreau panna cotta/passionfruit curd), ‘bits and bobs’ (mandarin and vanilla jam/smoked buttered popcorn/fairy floss) and ‘crunchy bits’ (peanut milk chocolate/coconut sable/choc streusel crumb/raspberry meringue/mandarin tuile).

If the prospect of intricately tailoring together an on-the-spot dessert feels like it’ll wear out the control pad settings in your brain, don’t worry – Gelato Messina has some off-the-rack sundaes worth trying.

There’s Cup of Life (which blends burnt vanilla and Fanta soft serve with mandarin jam, passionfruit curd, coconut foam doubling up on coconut sable, all served in – what else? – a cup); I Dough Know (burnt vanilla gelato piled on a donut base, with mandarin gel and tulle, mango foam and a drizzle of butterscotch sauce); Carni Candi Waffle (topped with a showy burst of fairy floss, this cone is crammed with Fanta sorbet, redskin custard, strawberries & cream jellies, all slathered in chocolate dip); Honey I Burnt The Kids (this was Will’s pick and definitely turns up the temperature on all the ingredients: it features burnt vanilla gelato with smoked chocolate fudge, burnt honey mousse and smoked butter popcorn – all in a cup); and Pavlova-kona, which powers up that iconic Australian flavour, by taking burnt vanilla gelato and passion fruit curd, then stacking it with a full deck of raspberry flavour – jellies, coulis and meringues – all scooped into a raspberry waffle cone. And that’s not even the whole menu.

Like you’d expect with any Gelato Messina offering, this establishment does come with pre-formed lines before you even get close to the front door. But Messina deserves a trophy for its queue management, because the waiting process is so orderly and efficient – you’re handed a menu beforehand to help fast-track your decision-making (so you don’t cause a traffic jam once you reach the front counter, slowing everyone down with your inconclusive, unthawed thoughts); and besides, the line moves briskly. Pretty soon, you’ve landed your newly constructed dessert and you’re feeling like a kid in an amusement shop.

If there’s another building boom, it’s going to happen here – created by an army of Messina diehards, experimenting with their latest ideal dessert.

And by the way, while this space used to be the location of the Gelato Messina Creative Lab, you can still order the birthday-worthy cakes here. But ignoring the appeal of a DIY sundae is going to be hard, even if you are on strict cake-pick-up duties.

Gelato Messina Dessert Bar, 243 Victoria St, Darlinghurst, NSW 1800 435 286 (1800 GELATO), www.gelatomessina.com/messina-dessert-bar.