I make mine with waxy potatoes always. In layers with crushed garlic scattered over each layer. Then I warm cream, add a bit of nutmeg, salt and grated cheese until it melts (gruyere is nicest) and then pour the mixture over the potatoes. Into a fairly hot oven till cooked.!
Waxy potatoes, rinsed in cold water after peeling. MIL, who is French, swears by creme fraiche which I think might be pretty standard across France since proper double cream can be tricky to find there. And Gruyere for the top!
Used to live in Lyon where you get a lot of dauphinois potatoes! My tips:
Use waxy potatoes Slice thin and blanch (or parboil but don't over cook) in salted boiling water if you want to save time. Use a metal tin for the crispiest results. Rub the dish with a cut clove of garlic and grease generously with butter. Mix milk and crème fraîche and add the cut garlic clove plus salt, pepper and nutmeg. Dip the potato slices in the milk mix and layer up in the dish. Dot each layer with butter and season generously. Pour the remaining milk/cream mix over the top, for with more butter and bake in a hot oven till the top is deep golden brown and crispy.
Definitely no cheese, if you are being authentic. (If it's well made it's better without!)
Half full fat milk/half cream with two crushed but still whole garlic clove scald in pan (bring it so it just boils up then straight off) remover garlic and leave to cool.
Make sure your slices of waxy potato are equally thin then layer carefully, salt/pepper/butter blob each layer.
Pour over cream/milk mix, cover with buttered foil (butter side down) and weight with something. Cook quite hot for 25 minutes weighted down with something that won't explode in the oven (!) (this gives it the nice solid/together feel you get in restaurants) then 20 minutes with the foil and weight off to get a nice golden crust.
I am not a particularly good cook but everyone loves and talks about "my potatoes"
Slice potatoes and layer with slices of thinly cut onions and season each layer with salt and pepper in large pot.
Pour on double cream almost to top of dish and cover in foil and put in oven at 180 fan for 3 hours. Remove foil for the last 45 minutes.
They are delicious and even better the next day. All, or most of the cream seems to be absorbed by the potatoes and is really easy and just put in oven and forget about it for 3 hours. Probably cooked by 2 hours but found one day when guests were late that it was better cooked for 3 hours lol.