Russian Potato Bread

This bread recipe was in a book on baking that my neighbour’s daughters gifted her for Mother’s day. She gave the book to me to copy a few breads that I might find useful and easy to bake. I am unable to give due credit to the author of this book because I have hurriedly copied the recipes and not the name of the book nor the author.
I quote what was in the book:
"In Russia, potatoes are often used to replace some of the flour in bread recipes. They endow the bread with excellent keeping qualities".
Ingredients:
225 grams potatoes
465 grams all purpose flour (I have again mixed whole wheat and all purpose flour)
15 grams fresh yeast
2 teaspoons salt
25 grams butter
Panning and baking the bread:
Cook potatoes until tender. Reserve the boiled water about 150 ml.
Mash the drained potatoes well.
Add warm water to the yeast and cover it. Allow to stand for about 10 minutes to rise.
Mix the flour, salt and rub in the butter. Add mashed potato and the yeast. Knead to a smooth dough adding the reserved water.
Knead for a further 8 to 10 minutes until smooth and elastic.
Place this is a lightly oiled utensil and cover allowing room for the dough to develop.
After about an hour when the dough has almost doubled in size, turn it on to a lightly floured board and knock back, punch and knead gently.
Shape this into a plump oval loaf of about 18 centimetres long.
Place on a baking tray. Sprinkle some bread flour over the surface.
Cover the dough with a lightly oiled cling film and leave it to rise in a warm place for 30 minutes or until doubled in size. At this juncture pre-heat the oven to 200 degrees C/ 400 degrees F/ Gas mark 6.
Using a sharp knife slash the top in diagonal cuts giving a criss-cross effect.
Bake for 30 to 35 minutes.
Remove and cool on wire racks.

Serve with a soup or just a tiny block of butter.