In a bowl of a stand up mixer, whisk together 2 cups of flour with 1.5 teaspoon dry yeast and 1 teaspoon salt.
In a blender, combine water, potato, melted butter and sugar. Blend until smooth.
Add the liquid mixture to the flour mixture, combine with a spoon until no dry spots remain. It will be shaggy.
Add 2 cups of flour. Fit mixer with a dough hook and knead until dough forms. Don't over mix. Einkorn might be sticky, spelt will be easily manageable, just slightly tacky.
Sprinkle with flour and give it a couple of hand kneads (it will firm it up and develop more surface tension).Cover and leave for 2-3 hours. The dough will increase in size significantly (probably triple).
Turn dough onto a well floured work surface. Sprinkle with flour, knead by hand for a minute or two, then shape into a ball.
Divide dough into 12 pieces.
Knead and shape each piece into a ball, and place on parchment lined baking sheet, seam-side down. Press lightly to flatten each dough ball.Cover with a tea towel. Allow to rest for 30-45 minutes.Preheat oven to 350ºF.
Brush buns with a beaten egg; sprinkle with sesame seeds.
Bake for 20 minutes, or until the tops brown nicely.