Combine the nuts, oats, potato, miso, sea salt, garlic, 1 cup and 2 tablespoons of the milk, and lemon juice in a blender and puree until very smooth.

Transfer mixture to a small/medium saucepan, and heat over low/low-medium heat for 5–8 minutes, stirring frequently until mixture starts to slowly bubble and thicken. To thin sauce slightly, stir in another 1–2 tablespoons of milk, or more as needed for desired consistency (it will thicken more as it sits as well). Avoid thickening sauce over high heat (or increasing heat too quickly), because this sauce can scorch easily.

Once sauce has thickened, transfer to a serving dish and serve. Alternatively, you can transfer to a baking dish and set under the broiler for a few minutes to lightly brown the top before serving.