Philly math teacher + bread baking. It all adds up for Zach Posnan.

Before the coronavirus created a baby boom of sourdough starters, Zach Posnan decided to give bread baking a whirl.

His first effort last summer was terrible, he said. “It didn’t rise. It was very dense. I actually had quite a few of those failures.” By winter, he gave up on it.

But earlier this year, a friend was having trouble with her starter — which at its core is simply flour and water — and asked Posnan to take a look. While helping, Posnan brought his to life. He stuck with it as his baking improved. Then came the shutdowns, giving Posnan, 39, a sixth-grade math teacher at Conwell Middle School in Kensington, more free time to experiment and get it down.

And get it down he has.

Working on his home oven, which maxes at 500 degrees, Posnan mastered the sourdough boule and moved on to wild stuff, all one at a time: There’s a boule made of hibiscus and lemon zest. There’s one that tastes like a Detroit-style pizza, stuffed with pepperoni and mozzarella with a crispy Parmesan bottom and top. There’s a boule with a half-pound of bacon inside. There’s a butterfly pea flour loaf stuffed with sun-dried tomatoes and feta that opens to a vivid purple, even before the Instagram filter is applied. He also makes sourdough soft pretzels stuffed with a variety of sweet and savory ingredients, such as chocolate, fruit preserves, peanut butter, and sweet cream cheese.

There’s also a plain boule — his bread and butter, you might say — with a chewy crust and an elastic sponginess inside. Slice off a piece, pop it into the toaster, and you’ll find enough crunchy nooks and crannies to stand up to anything you spread on.

As friends started placing orders, Posnan set up an ordering form on Instagram, where he calls his fledgling operation Brass Monkey Bread Co. Pretzels are three for $10 to $15, breads are $10 to $15.

As with baking, timing is everything. Shortly after he begins accepting orders at noon Sunday, he is sold out. Customers pick up their loaves and pretzels in the Point Breeze neighborhood and in the Cheltenham and Abington area on appointed dates.

One bread fancier who ordered every week contacted Posnan because he was going out of town and wanted to take loaves with him so his in-laws could try it. Posnan did a custom bake, and the grateful client paid for additional loaves to cover the missed week. Posnan has been paying things forward anyway, giving loaves to groups such as Everybody Eats.

Posnan added pretzels to his repertoire for two reasons: “I love soft pretzels, and one of the things I do for my students is go to Center City Pretzel Co. on Washington Avenue once a month. Because they open so early, I can get fresh pretzels when I leave my house at 6:30. I was also looking for something to do with my discard. The pretzels use the castoff from my feedings.”

For now, Posnan will juggle teaching and baking. Eventually, he would like to open a small bakery, perhaps in Point Breeze near his home.

Posnan says the secret is patience. “A lot of people will expect their starters to take off in the first week. It really takes about two to three weeks for it to really start to grow and mature. It’s a lot of work when you’re doing sourdough. You have to feed it every day.”