Preheat the oven to 400
Put the cheese in the freezer for 10 minutes, then grate on the large holes of a box grater; set aside.
Use the slicer on you box grater to thinly slice the potatoes (or you can use a mandoline).
In an oven-proof skillet, melt the butter over medium to medium-high heat. Add the onions; sprinkle with salt, pepper, herbs de provence, thyme salt and pepper. Stir often and sauté until onions are soft; about 5 minutes. Add garlic and stir for another 30 seconds.
Add cream and chicken stock; bring to a boil.
Turn off the heat and mix in most of the chives and half of the grated cheese.
Arrange the potato slices in the pan keeping them as vertical as possible.
Bake for 40 minutes.
Sprinkle the remaining cheese on top of the potatoes and bake for 10 more minutes until the cheese is melted and there is a golden brown crust.
Garnish with remaining chives and serve immediately.