Boil the potatoes for 15-20 minutes, or until slightly soft. Remember to wash them before. When they are soft, remove them from the heat, drain them, and cut them into slices.
Grease a medium ovenproof dish with butter while the potatoes cook. Take advantage and also spread the entire base with a little garlic sauce so that the dish of scalloped potatoes takes on a good flavor. Set aside. To make the garlic sauce you can buy it already made in any supermarket.
Mix the melted butter with a little garlic sauce. You can use half a teaspoon in this step and half in the previous step, although the amount is to taste. Reserve this garlic butter and you can now preheat the oven to 200 ºC.
Prepare the cream to further enhance the recipe for baked potatoes au gratin. To do this, season the milk cream with BBQ sauce, salt and pepper to taste.
Assemble the potatoes au gratin. To do it correctly, recover the previously greased mold and place the ingredients after layers. Start with a layer of potato slices, a little butter, and another layer of cream.
Repeat the process until you finish with all the ingredients. The potato pie au gratin should end with a layer of cream.
Spread the Parmesan cheese all over the surface and cook the potatoes in the oven until the cheese is gratin. It is best to use Parmesan cheese, but you can use any other of your choice, keeping in mind that the ideal is that it is a cheese that melts when you see a golden coating, the potato gratin is ready. Serve warm.