I cooked a gratin dauphinois: basically sliced potatoes covered with a mixture of cream and milk baked in an oven for about an hour.
The taste was good, the texture of the potatoes was good, but the dish did not stay together. When cutting a piece of the dish, I barely managed to move it to a plate and it kinda slid into pieces. It is as if the dish was too liquid and nothing kept the potatoes together.
When I have it at a restaurant, it is a compact dish: layers of potatoes held together that you can cut without the slices trying to escape. If you look at https://youtu.be/Gv0BroAQcG8?t=3 this is what it should like (the dish is not exactly gratin dauphinois and there is no cheese - but it is how it should look like and behave).
I did not wash the potatoes after slicing them (hoping that the starch would be enough to hold them together) but it was apparently not enough.
What can I do to "solidify" my dish?