Preheat oven to 400°F. Prepare a baking sheet with silpat or parchment paper.
Thinly slice potatoes, approximately ⅛” thick. Using a mandoline here will make the job easier.
Toss potato slices with oil and evenly spread on a single layer on the baking sheet.
Bake potato slices for 25 minutes.
In a saucepan over MEDIUM heat, melt avocado oil, shallot, and garlic until shallot is translucent (1-2 min).
Add flour, and cook an additional 1-2 minutes.
Whisk in broth & milk, adding small amounts at a time.
Stir until the mixture thickens, and allow to boil for 2 minutes.
Season with salt and pepper.
In a baking dish, layer prebaked potato slices and cream sauce. Finish with a cream sauce layer on top.
Cover and bake for 10 minutes. Uncover, and bake for an additional 5 minutes.
Allow dish to rest for 10 minutes. Garnish with fresh herbs.