Lightly grease a large oval baking dish. Using a mandolin or sharp knife, slice the potatoes into thin slices, about 3mm thick. Tip into a bowl and coat with the melted butter, oil, herbs and some seasoning.
Tightly pack the potatoes upright into the dish. Wedge some bay leaves throughout and pour over the remaining butter mixture from the bowl over the top. Cover with foil and bake for 30 mins at 200C/180C fan/gas 6.
Remove the foil and cook for a further 45 mins at 220C/200C fan/gas 7, until the potatoes are cooked through.