Potato Sourdough Milk Buns

felt like having fish burgers so decided to make buns for the fish. I’ve had some luck with using potato so decided to add some mashed potato to my milk bread for buns. Both the potato along with the tangzhong should made very soft buns.
I was watching a YouTube video recently that sought to dispel the idea that tangzhong should be made at a 1:5 ratio of flour to liquid. In fact, the author suggested based on studies done with tangzhong and yudane that the ratio should be closer to 1:1-1:2. They also suggested that ideally the percent flour from the tangzhong or yudane should approach 20%. With a 1:5 ratio and 20% flour in tangzhong would leave essentially no liquid left to prepare the dough with. However, at 1:2 or less there would be liquid left. So this is my first bake using a lower ratio of 1:2 flour to milk but at 10%, which is higher than my usual 7%. I will gradually adjust the tangzhong over time to see if there is any discernible improvement to the bread. I figured that this was a good start.



For 8 buns about 65 g each

egg wash: 1 yolk, 1 tbsp milk and a pinch of salt, beaten…

Instructions
Levain
Mix the levain ingredients in a jar or pyrex container with space for at least 300% growth.
Press down with your knuckles or silicone spatula to create a uniform surface and to push out air.
At a temperature of 76ºF, it typically takes up to 10-12 hours for this stiff sweet levain to be at peak. For my starter I typically see 3-3.5 times increase in size at peak. The levain will smell sweet with only a mild tang.

Tangzhong
In a sauce pan set on medium heat, stir the milk and flour until blended. Then cook for several minutes until well thickened, stirring regularly with a spoon or heat-resistant spatula. Let cool in the pan or, for faster results, in a new bowl. Theoretically it should reach 65ºC (149ºF) but I don’t find I need to measure the temperature as the tangzhong gelatinizes at this temperature. You can prepare this the night before and refrigerate it, ensure that it is covered to prevent it from drying out.

Dough
In the bowl of a stand mixer, add the milk (consider holding back 10 g of milk and adding later if this is the first time you’re making this), egg, tangzhong, salt, sugar and levain. Mix and then break up the levain into many smaller pieces. Next add the flour, I like to use my spatula to mix until there aren’t many dry areas. Allow the flour to hydrate (fermentolyse) for 15 minutes. Mix on low speed and then medium speed until moderate gluten development this may take 5-10 mins. You may want to scrape the sides of the bowl during the first 5 minutes of mixing. Next drizzle in the melted butter a little at a time, or alternatively add room temperature butter one pat at a time. Slow the mixer down to avoid splashing the butter at you. The dough may come apart, be patient, continue to mix until it comes together before drizzling or adding in more butter. Once all the butter has been added and incorporated increase the speed gradually to medium. Add the mashed potatoes gradually. Mix at medium speed until the gluten is well developed, approximately 10 mins. You will want to check gluten development by windowpane during this time and stop mixing when you get a good windowpane. You should be able to pull a good windowpane.
On the counter, shape the dough into a tight ball, cover in the bowl and ferment for 2.5-3.5 hours at 82ºF. There should be some rise visible at this stage.

Line a large cookie tray with parchment paper. Punch the dough down and then divide into 8 equal portions. Form each into tight boules. Place on a parchment lined cookie tray. Cover them and allow them to fully proof about 4-6 hours, they should pass the poke test.

After about 30 mins of proofing time, whisk your remaining egg and milk and then brush the small boules.

About 30 mins prior to end of final proof preheat the oven to 350°F.
Immediately prior to baking brush the dough again with the egg and milk mixture. Spoon sesame seeds onto the buns, spread then press lightly with a finger.

Bake the buns uncovered for 30-35 minutes or until the internal temperature is at least 190F. Cover if your rolls get brown early in the baking process.

Remove the buns from the oven and transfer to a rack to cool.