Preheat the oven to 350F/175C. Heat a pan, add oil, garlic, salt and pepper. Fry for about 1-2 minutes often stirring.

Add flour - one spoon at a time, let it mix in before adding more. Fry for another minute.

Gradually add milk, stirring all the time. Once all the milk is in, add broth and mix it all together.

Lower the fire, and stir often for another 4-5 minutes.

Transfer the sauce to a blender, add salt, pepper, and yeast.

Mix everything till you get a creamy mass. Taste and add more spices if needed.

Grease a baking dish, put half of the potato slices inside, stir in salt and pepper, even them, and sprinkle with 15g parmesan.

Add the rest of the potatos, sprinkle the rest of the parmesan, and pour in the sauce. It should cover all of the potato slices.

Cover with aluminium foil and bake for 20 minutes. Take off the foil and bake for 40-45 more minutes.

Cool for 10min before serving.