The writer Elizabeth Carter describes in her book Majorcan Food and Cookery how these light buns for morning coffee or teatime are often made with the pulp of sweet potatoes but may also be done with the ordinary potatoes that we can buy everywhere.
Bake the potatoes in their skins, then peel them, discarding the skins. Mash the potato pulp with a fork.
Cream the yeast in the tepid milk. Mix the flour and potato pulp in a bowl with the sugar. Rub in the lard.
Make a well in the centre and add the yeast liquid. Add the egg and mix to a dough. Adjust the texture by adding more milk or more flour. Potatoes will vary in their take-up of liquid. The dough should be moist but not unworkable.
Turn the dough on to a floured work surface and knead for 5 minutes.
Leave the dough to rise in a bowl covered with oiled clingfilm in a warm place (24°C/75°F) for about 1 hour, until doubled in size.
Turn out on to the lightly floured work surface and divide it into eight pieces. Shape these into round balls and place them well apart on a greased baking sheet. Cover with oiled clingfilm and leave to prove for 30 minutes, until they have again doubled in size. Meanwhile, heat the oven to 400°C/200°F/gas 6.
Bake in the oven for about 15 minutes, until the buns are nicely browned. Cool on a wire rack.