Boil the potatoes, uncovered, in salted water for approx. 20 mins. until soft. Drain the water, shake the pan so that the residual moisture on the potatoes evaporates, leaving them whitish and dry. Push the potatoes through a sieve into a bowl. Stir in the yolk, olive oil and cornflour, season.
Shape the mixture into 3 balls, flatten slightly, pulling the edge up a little, place 1 tbsp of bolognese on each, wrap in the dough and shape into balls. Roll the balls in the flour, shaking off the excess flour, then coat in the egg then the breadcrumbs. Heat the peanut oil in a pan to approx. 170 °C. Place the balls in the oil in batches using a slotted spoon, cook for approx. 5 mins. until golden yellow, remove and place on kitchen paper to remove excess oil. Halve the balls and divide onto 2 plates.