Preheat the oven to 350 and spray a 9x13 pan with cooking spray.
Peel the potatoes and then cut into ⅛ “ slices. Use a mandolin slicer if you have it.
In a large stock pot, heat the water and the bouillon until boiling over medium heat. Add salt to the water. When water is boiling, gently add the potato slices to the water and return to a slow boil.
Cook the potatoes in the boiling bouillon water until the potatoes are nearly cooked through. Should retain some of the crunch in the center. Do not overcook them till they are soggy and falling apart -0 this is just a pre cook. Every few minutes, GENTLY turn the potatoes in the pan using a large spatula. Use care not to break the potatoes.
While the potatoes are cooking, in a separate sauce pan combine the butter, cream, Gruyere and cream cheese and cook over medium heat until all are melted. Stir frequently to keep it from burning/sticking to the bottom of the pan. Whisk out any lumps.
When the potatoes are nearly cooked through and the cheese is melted, gently scoop the potatoes into the 9x13 prepared pan (use care not to break) and pour the cheese sauce over the potatoes until you have either poured all of it over or until the level of the cheese sauce reaches the top of the potatoes. You may have extra cheese left over.
Bake at 350 until the sauce is bubbly throughout, the potatoes are cooked through and a slightly browned crust develops on the top - about 35-45 minutes.