Peel the potatoes and cut them very thinly into slices (here with a mandolin).
In olive oil, brown the chopped shallots for a few minutes, then the crushed garlic.
Add the potatoes and then the rest of the ingredients.
Cover and cook for 10 minutes, stirring regularly.
Preheat your oven to 200°.
Divide the mixture in a gratin pan and bake for 35/40 minutes until the flesh of the potatoes is cooked (check with the tip of a knife, it will depend on the thickness of your potatoes).