Former clinical medical technologist Katherine Yeap, 44, loves sourdough so much, she curated the entire menu at her bakery Cornerstone Bakes to feature assorted breads characterised by the dough’s quintessential tang. This means she offers not just the usual rustic boules (round loaves), but also items like sourdough cinnamon rolls, bagels, Japanese-style shio pan (salted crescent-shaped soft buns) and milk buns.

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Her day starts at 6am & ends at 10pm

Occupying a small space on the ground floor of One Dusun Residences in Balestier, the bakery opened in December 2021. It’s a one-woman show here — the reticent Katherine does everything herself, from baking all the breads to washing up. Her day usually starts at 6am and ends at 10pm. “It's hard work, but to me it's also fun and gratifying,” she shares. 

From clinical medical technologist to baker

Before becoming a baker, Katherine worked in the healthcare industry, where she handled blood, urine, stool samples and other body fluids in hospital labs. It wasn’t until she wanted to spend more time with her two children, now eight and seven years old, that she decided to leave the industry in 2015. 

As a homemaker, she began experimenting with baking. When her daughter was two, Katherine baked a birthday cake for her and her school mates. It was a hit. “So I started making cakes from home for my friends and family upon their requests,” she shares.

She subsequently enrolled in a baking course that taught her how to make sourdough breads. As her children grew older, Katherine had more free time and wanted to return to the workforce. 

“I’ve always wanted to work in F&B,” she says, adding that growing up in a family of foodies (the Singapore PR grew up in Penang) may have influenced her decision to open her own bakery.

Katherine’s love for sourdough bread started as an undergraduate in Australia, where she frequented bakeries there. “The idea of baking bread came naturally, and we managed to find a shop unit right within the condo near where we are staying,” explains Katherine. 

Since she lives near her shop, her kids pop by to visit her often.

Why sourdough? 

Katherine finds the chemical processes within a sourdough bake intriguing. She was given her sourdough starter by her baking instructor, who had gotten it overseas. According to Katherine, the starter she uses now is supposedly “more than 100 years old.” She adds: “Working with a ‘living dough’ is fascinating and to see it evolve into delicious bread is gratifying”. One habit the ex-clinical med tech brought over from her previous job is her obsession with precision. Katherine laughs: “Measurements at my bakery are almost always measured to the dot."

"Of course, I prefer working with bread now because I don't have to thoroughly clean myself after work, and I can hug my kids anytime,” she shares.

So, what makes sourdough, sourdough?

Unlike most bread types, sourdough doesn’t use commercial yeast to rise. Instead, it uses a starter, also called levain, which comprises wild yeast and good bacteria. Water and flour are added to this starter to form a dough that ferments with time. The yeast or bacteria doesn’t produce its prominent sourness. Rather, the fermentation produces lactic and acetic acid as by-products that result in the bread’s characteristic tang. Sourdough is generally believed to be one of the healthier breads around and beneficial for gut health.

The menu

Katherine bakes between five and six different variations of sourdough loaves in the bakery daily. “They are seasonal,” she shares. When we were there, there were olives, black sesame, fruits and nuts to list a few. In other instances, customers can even take home one made using longan, red dates and Chinese herbs, or carrot and raisins.  

As mentioned, aside from classic country-style loaves, there’s also sourdough bread in less common forms: soy milk buns, bagels, Japanese-style shio pan and even cinnamon rolls, all made from the same sourdough starter. Beyond these bakes, there are also sourdough cookies and strangely enough, jellies. 

Olive Sourdough Loaf, $9.80

Cornerstone’s rustic oval sourdough loaves are a little lighter-crumbed than your traditional dense European sourdough. This one boasts a nice golden-brown crust that conceals a rather airy interior studded with green and black olives. We suspect the less heavy texture will appeal more to Asian palates. The bits of fruity, salty olives offer a good contrast to the sourdough’s tanginess.

Black Sesame Sourdough Loaf, $9.80 (8 DAYS Pick!)

Here, Katherine folds in a generous serving of black sesame seeds and paste into the dough before letting the oven work its magic. The result is an aromatic and visually captivating loaf — easily our fave among the ones we sampled. 

This is a savoury bread with great texture. It has a firm, crusty exterior mottled with black sesame seeds and an airy interior brimming with black sesame paste, making it slightly gritty. The complex blend of nutty roastiness and delightful tang is lovely. Pop this into the toaster for maximum pleasure.

Sourdough bagels steamed instead of boiled before baking

While the bakery offers a variety of sourdough bagels, from chocolate to oat, matcha and cheddar to blueberries, customers can only find two types of bagels each day. 

Traditionalists would argue that the “bagels” here are not, in fact, really bagels because Katherine doesn’t boil the dough in water first before baking them. But she begs to differ. “The oven we use has this steaming function that can substitute the boiling process, and they can still achieve the same consistency,” she explains. True enough, we found the dense and chewy mouthfeel of these pudgy bakes quite similar to regular bagels.

 

Oats Sourdough Bagel, $2.50 (8 DAYS Pick!)

The oat-infused option has a thin and crisp exterior which offers a nice crunch and earthy nuttiness to the sourdough’s characteristic sourness. Its mouthfeel i ultra-chewy, as you’d expect from a bagel. In this case, using the sourdough starter adds a nice depth of flavour. Pretty good.

Chocolate & Chocolate Chunk Sourdough Bagel, $2.80 

This moist and dense bagel is made using chocolate powder and dark chocolate chunks from Belgium brand Callebaut. When sliced, it features an almost gooey chocolate centre. But we find the bittersweet choc clashes with the tangy sourdough. 

Matcha & Cheddar Cheese Sourdough Bagel, $2.80

East meets west in this number featuring grassy, slightly bitter matcha paired with creamy and mildly salty cheddar cheese cubes. We’d have preferred it if it were just plain matcha or cheese since both of them didn’t quite work together with the sourdough.

Olive, Cherry Tomatoes and Rosemary Sourdough Mini Bread Rolls, $1.20 

Garnished with rosemary, the mini bread roll cushions a cherry tomato between two black olives. Very piquant and quite juicy. The bun is pretty fragrant on its own, too, with a delightful fragrance from the rosemary. 

Cinnamon Roll, $2.50 

We’ve never tried cinnamon rolls made with sourdough starter, so this was rather intriguing. The ones here aren’t drowned in a sugary glaze, and are reasonably fluffy – though they’re still denser than classic cinnamon rolls. The contrasting sourdough tang and sweetness from the melted brown sugar was a bit confusing — and it needed a heavier hit of cinnamon and butter.

Bottom line

Aside from the excellent Starter Lab, it’s not often you find a bakery that sells almost exclusively sourdough bread in various incarnations. Go for Cornerstone’s rustic loaves with unusual flavourings like sesame — their crusty, lighter-than-usual texture will appeal to those who love sourdough but have weaker teeth. Among the other sourdough bakes here, we enjoyed some of the chewy bagels, like the oat-flecked one (but skip the chocolate and matcha with cheese).

The details

Cornerstone Bakes is at #01-17 One Dusun Residences, 1 Jln Dusun, S329363. Open daily except Sun, 11am-6pm. 

Photos: Lionel Lai

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