2 Tbsp dairy-free butter
1 medium onion, minced
2 medium garlic cloves, minced or pressed
1 Tbsp fresh thyme leaves, minced
14 - 1/2 t nutmeg
1 1/4 tsp Celtic salt
1/2 tsp ground black pepper
1 1/2 lbs (about 5 med) russet potatoes, peeled and sliced 1/8" thick
1 cup vegetable broth
1 cup rice or nut milk
2 bay leaves
1. Adjust an oven rack to the middle position and heat the oven to 425 degrees.
2. Melt the butter in a Dutch oven over medium-high heat. When the foaming subsides, add the onion and cook, stirring occasionally, until soft and lightly browned, about 4 minutes. Add the garlic, thyme, salt, and pepper and cook until fragrant, about 30 seconds. Add the potatoes, broth, milk, and bay leaves and bring to a simmer. Cover, reduce the heat to medium-low, and simmer until the potatoes are almost tender (a paring knife can be slipped into and out of a potato slice with some resistance), about 10 minutes. Discard the bay leaves.
3. Transfer the mixture to an 8-inch square baking dish (or other 1 1/2 quart gratin dish). Bake until the top is golden brown, about 15 minutes. Cool 10 minutes before serving.