Mix the yeast with lukewarm water, add the mashed potato, salt and flour. Knead the dough but not to much, it's supposed too have a soft consistency. Let the dough rest for 35-40 min.
Put some flour on your working table. Knead in a little bit more flour and cut the dough in 10 pieces. Roll the dough into circles. Let them rest for 10 minutes on a baking sheet with flour.
Pour 3-4 cm oil into a pan or pot, heat the oil to 360F (180C). Test fry a little bit of dough.
Fry the langos one at the time for 3-4 minutes on each side until it has a golden brown color. Let them rest on a grid with paper underneath. (You can add the cheese now if you want it to melt on the langos)
Garlic oil
Mix the grated/pressed garlic with olive oil. Brush the langos with the oil.
Topping
Add garlic and salt the sour cream or crème fraiche, then add it on top of the langos.
Cook some bacon and chop it up together with the red onion. Add it on top of the langos along with your favorite cheese!