Darwin Su grew up in Indonesia, the birthplace of tempeh.
"If you go to a traditional market every morning, they have fresh tempeh and it's still warm, it's still wrapped in banana leaf," he says. "Tempeh is a national treasure."
Like tofu, the fermented soybean protein is a nutritional powerhouse that's affordable and available across much of the archipelago.
"Every city in Indonesia has completely different types of tempeh," he says. In Medan, North Sumatra, where the chef was born, the local cuisine has Indian influences – so tempeh was cooked with a heavy amount of spices, like cumin and chilli.
In Jakarta, where he later lived, tempeh was braised with coconut, palm sugar, ginger, spices aplenty and lime or curry leaves. Order this highly fragrant ingredient from a stall, and the vendor would deep-fry it. "It's so good. All the flavour is soaked up in the tempeh," he says. "You just eat it with rice and sambal."
At home, his mother would make tempeh orek: the soybean pieces turning crisp and sweet from the soy sauce and the high heat of the pan.
"In central Java, they have this tempeh where they over-ferment it, so it becomes black," he says.
The chef hasn't tried it, but he sells his tempeh to a customer from Java and she's keen to leave it out and (safely) age it in a similar way.
Despite growing up with a pro-tempeh diet in Indonesia, Su never thought of fermenting soybeans until recently. "You don't make tempeh at home because you can just buy it at the market."
It wasn't until he was working at Banh Xeo Bar in Sydney (a job he's held for nearly two years), that tempeh production crossed his mind. Last June, his head chef Ben Sinfield gave him The Noma Guide to Fermentation as a birthday present. Soon Su, was experimenting with miso, pickles, koji, garum and other fermented foods – everything except tempeh.
But when Sydney went into a COVID-19 lockdown earlier this year, the chef realised fermenting the Indonesian staple would be a good side business – especially as "I know how fresh tempeh should taste like". He subjected his friends to his experimental blocks – and they loved it. And so, Ferments' Lab was born.
Su says, "Traditionally, the way they make it, they step on the beans. I think it's like how to make wine. Indonesia is already hot, they don't need the incubator or whatever, they leave it out and it just ferments by itself."
For Ferments' Lab though, he soaks and cooks his beans (no toe-stomping necessary). Once cool, he combines the ingredient with apple cider vinegar, then mixes in his starter (rhizopus oryzae) and lets the beans ferment. Soon it starts to resemble a rice cake. Once ready, you have three days to enjoy the tempeh – or you can braise it to make it last longer, like his mum did with sweetened soy sauce in Indonesia. "It's like curry," he says. "Curry tastes better the next day – or two or three days."
While tempeh is typically made with soybeans, Su has been producing the protein with a rainbow of ingredients: black turtle beans, green peas, chickpeas and buckwheat.
A vegan tempeh-maker in Amsterdam inspired him to sprinkle toasted black sesame seeds throughout his chickpea version, while the Australian landscape sparked the idea of creating the Indonesian staple with macadamia nuts. Adzuki beans, traditionally used in Japanese desserts, have ended up in his tempeh-making attempts; flaxseed has also been scattered through.
"I just like to experiment," he says. "My intention was [also] to cater to people who have soy allergies."
The different varieties also have contrasting flavour profiles. The chickpea tempeh has a subtle creaminess, while the green pea version has an umami sensation, like a muted blue cheese. The black turtle bean flavour has a bright punch to it, and it crisps nicely in a pan. The buckwheat version generates distinct flavour pops in your mouth.
Su isn't just playing around with tempeh, either. His rye bread miso tastes like nasu dengaku when spread on toast, while his zesty version of Japan's yuzu kosho chilli condiment features pear and lemon instead of Japanese citrus. Meanwhile, his egg white amino sauce (created from surplus ingredients from Banh Xeo Bar's mayo-making sessions) and his porcini mushroom shoyu are both gluten-free experiments in making soy sauce. And he's embracing Indigenous ingredients by producing a wattleseed miso.
These condiments will take months to develop, but in the meantime, people can buy tempeh directly from Su via direct messaging him on Instagram.
His customers include cookbook author Holly Davis, people across Sydney and many local Indonesians.
Although they're loyal, they don't stay around to chat like his non-Indonesian customers, who often have many questions about the ingredient.
"I guess with Indonesians, they already know what tempeh is – they just buy and that's it!" he says and laughs.
For more info, follow Darwin Su on the Ferments' Lab Instagram.
This is a very traditional Indonesian cake that is grilled layer by layer in the oven, but the results are impressive and totally worth it.