Add a little warm water and sugar to the yeast in a glass and leave it until it foams.
Mix into the flour, add the mashed potato and slowly mix in the water. Add a large pinch of salt and knead for ten minutes.
Leave to rise until doubled in size, knock back the dough and spoon into a nine hole fairy-cake tin. Leave to rise again for another fifteen minutes and bake at 220c for 15-20 minutes.
Meanwhile, make the mini burgers by mixing together all the ingredients except the cheese. Divide into 9 balls and put a cube of cheese in the middle of each. Form the mince around the cheese and shape into burgers.
Heat a griddle pan to high and cook the burgers for about 4-5 minutes on each side. Slice the buns in half and serve each mini burger with sliced red onions, tomato and lettuce.
For the bread:
400g bread flour
150g plain flour
250g peeled, cooked and mashed Maris Pipers
7g dried yeast
Pinch of sugar
300ml warm water
Pinch of salt
For the burgers:
650g lean beef mince
1 egg, beaten
Leaves from 1 thyme sprig
70g strong blue cheese such as Stilton
Salt and pepper