In a mixing bowl sift the flour. Make a well in the middle and pour 1/4 cup lukewarm water. Sprinkle the yeast and leave at room temperature until the yeast is dissolved and it foams, like a sponge.
When the yeast is proofed, add the egg, mashed potatoes, butter and salt.
If you’re using a stand up mixing, with the dough hook on, start mixing slowly adding 1/2 cup water and keep mixing until the dough comes clean from the sides of the bowl.
If you’re mixing by hand, use a Danish whisk or a wooden spoon and slowly add water in the middle of the flour mixture until the dough is formed.
Take the dough out of the bowl (no mater if you’re using a stand-up mixer or a Danish whisk) and place it on a floured working surface.
Knead by hand until it becomes smooth and elastic, about 5-7 minutes.
Place the dough into a floured or oiled bowl, cover with plastic wrap and leave at room temperature until doubled in volume.
Take the dough out of the bowl, place it on a floured surface and divide it into 8-12 buns, depending on how small/big you want the buns.
Place the buns on a baking sheet, cover and leave at room temperature until almost doubled in size.
Meanwhile heat the oven to 375F.
Just before putting the buns in the oven, brush them with egg wash (egg yolk mixed with water)
Bake for 25-30 minutes until golden. Leave to cool slightly before removing them from the baking sheet.
You can store the buns in the fridge or in the freezer. When ready to use again, just heat the oven to 350F and place the buns in the oven for few minutes until warm. Or you can microwave them for few seconds