There is nothing quite so satisfying as biting into a warm, grilled cheese sandwich and watching as the crispy, golden exterior makes way for a long, stretchy pull of melted cheese.

The staple sandwich, which has mesmerised diners since the Great Depression, has achieved such a state of reverence in its origin country of the United States they’ve dedicated a day to it: National Grilled Cheese Sandwich Day, on April 12.

To celebrate this hallowed day, Sydney’s patron saint of cheese toasties Penny Lawson (of Penny’s Cheese Shop at Potts Point) has generously shared her secret to creating the ultimate grilled cheese.

The self-professed “curd nerd”, who serves as a cheese judge across Australia, has earned a cult following for her cheese toastie ($15): A complex and ever-evolving blend of up to seven cheeses, served on sourdough from PiOik Bakery.

The current iteration features cheddar, sfogliato da mucca (a pasta filata cheese), Gruyère, raclette, queso oaxaca and smoked scamorza. But this is not cheese for the sake of cheese - each serves its own purpose, from the foundational savouriness of the cheddar, to the sweet nuttiness of the Gruyère, to the theatrical pull of the raclette.

“Each cheese brings a different element to the party,” Lawson explains.

There are just 50 grilled cheese sandwiches made at Penny’s each day, and on weekends they frequently sell out before noon. Among its fans is UK actor Liam Neeson, who received a Penny’s Cheese Shop care package while in hotel quarantine during the height of the COVID pandemic.

“He was very appreciative,” says Lawson. “He wrote us a lovely note that said it was the best cheese toastie he’d ever had. It was a real thrill!”

Ready to up the ante at home? These are Lawson’s top tips.

Recycle your cheese rinds

Ground cow’s milk cheese rinds are an unlikely addition to the cheese blend at Penny’s. They were first introduced as a way to reduce waste in the kitchen, before Lawson realised the deep flavours of umami they brought to her cheese toastie.

Choose your bread carefully

Lawson swears by the sourdough at PiOik Bakery. It’s a blend of rye and wholewheat that undergoes a three-day fermentation process to create a chewy, flavourful loaf. Lawson advises using day-old bread for the perfect texture.

“It has a better Maillard reaction [when placed on the pan], you get a nicer browning and crispiness,” she says.

Ditch the mayo and the butter

The secret to creating the perfect golden, crusty exterior is not (as famously reported by New York Times writer Julia Moskin) the liberal spreading of mayonnaise (or butter) on the pan-side of each bread slice, claims Lawson.

“Never put mayonnaise on the outside of a toastie,” she urges.

“It might look good in a photo, but the flavour of warm mayo is awful.”

Rather, Lawson lightly spreads a small amount of the cheese mixture on the sandwich exterior before pan-frying.