Creamy Scalloped Leek & Potato Gratin

With a creamy sauce and a crispy crust.

2 bunches leeks 4 cloves garlic 4–5 sprigs robust herbs 2 large handfuls soft herbs 1½kg potatoes 2.1½ cups semi-hard cheese 3.2 lemons ½ cup extra virgin olive oil salt and freshly ground pepper ¼ cup apple cider vinegar 2 Tbsp sugar 1 cup fresh cream