Add your potato flakes to a small bowl. Take ⅔ of your water (⅔ cup or 160g/ml) and microwave it until just boiling.
Pour the boiling water into your instant potatoes and mix. They might look slightly dry but mostly like mashed potatoes. Let cool for about 5 minutes.
In the bowl of your stand mixer with dough hook attached, add flour, mashed potatoes, salt, yeast, sugar, egg and remaining ⅓ cup/80g water and mix on low until a rough dough forms.
Add your soft butter, and mix until fully incorporated.
Allow the dough to knead until smooth and elastic (10-20 minutes). Dough will be sticky but stretchy.
Remove dough from bowl, lightly grease bowl, shape dough into a ball and place back into the bowl. Cover and allow the dough to rise in a warm spot for 1-2 hours or until doubled in size.
Line a baking sheet (preferably a half sheet - 13x18 inch but at least a 9x13) with parchment paper. Set aside.
When dough is ready, punch down the dough and remove from bowl onto workspace. Divide the dough into 8 equal portions. My dough ended up with portions weighing about 90g each, however weighing is not a requirement.
Take a portion of dough and stretch and fold the sides into the center creating a rough ball shape. Flip the dough ball over onto your work space with the seam side down and cup your hand over the dough. Using a circular motion, gently move the dough, to help create a more uniformly round ball with tension in it.
Place the dough ball onto your bake sheet and repeat the process with all the remaining dough portions.
Once all the dough has been shaped, gently use your hand to very lightly pat down the dough balls. You aren't completely flattening them, but just removing a little bit of height so they are less spherical.
Cover your baking sheet and allow your buns to proof for 30-45 minutes or until dough has puffed up a bit.
While your dough is proofing, preheat your oven to 350°F.
Optional When dough is ready, brush all the buns with egg wash and sprinkle with sesame seeds (poppyseeds could also be used).
Bake your buns on the center rack of your oven for 20-22 minutes or until buns are golden brown and sound hollow when the bottoms are tapped.
Remove from oven, and transfer buns to wire cooling rack. Allow buns to come to room temperature before slicing and enjoying!
