Heat butter in a medium sauce pan. When butter has melted, whisk in flour to create a roux. Continue to whisk until mixture turns a very light brown and has a nutty smell, approximately 4-5 minutes.
Whisk in half & half, then add shallots, garlic, rosemary, parsley, thyme, fine sea salt, white pepper and 1/2 cup shredded Swiss cheese. Remove from heat and set aside.
Coat a 9-inch pie plate with cooking spray. Layer potatoes in a circular fashion. After you complete one layer, cover with just enough half & half mixture to cover it. Repeat layers until potatoes reach the lip of your pie plate. Pour remaining half & half mixture over potato slices.
Bake, uncovered, for 50-60 minutes or until potatoes are tender and mixture is bubbly. Remove and cover with remaining 1/2 cup Swiss cheese. Return to the oven until cheese has melted, approximately 5-10 minutes.
Remove and allow to set for 5 minutes. Slice and serve.
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