Mushroom Basil Au Gratin (from Straight Up Food)
Once you have all your ingredients chopped and ready to go, this recipe comes together in a breeze!
Ingredients for the casserole:
- 1¼ pounds russet potatoes (2 to 3 medium), peeled and thinly sliced
- 1 medium yellow or white onion, halved and thinly sliced (about 1½ cups)
- ½ pound medium white or cremini mushrooms, thinly sliced (about 1½ cups)
- 4 cups coarsely chopped Swiss chard or spinach
- 1½ cups chopped fresh basil (about 40 medium-large leaves)
Ingredients for the sauce:
- 2 cups unsweetened soy or almond milk
- 2 ounces raw, unsalted cashews (about ½ cup)
- 1 tablespoon dried Italian herb seasoning
- 1 teaspoon granulated onion
- ½ teaspoon granulated garlic
- To make the sauce, place all of the sauce ingredients (soy or almond milk, cashews, Italian herbs, and granulated onion and garlic) into a blender, and set aside (so the cashew can soften).
- To slice the potatoes thinly and uniformly, a mandolin slicer works best. If you do not have a mandolin, use a chef’s knife and aim for about a ⅛-inch thickness. Place the sliced potatoes, onions, mushrooms, and chopped chard/spinach and basil each into their own bowls.
- Preheat the oven to 375°F. Set aside a 13×9-inch baking dish (you do not need to use a greased pan or parchment paper).
- Blend the sauce thoroughly until smooth.
- Prepare the casserole by creating layers in these next steps (5-9). Start by pouring a thin layer of sauce into the dish so it coats the bottom evenly.
- Layer one-third of the potatoes across the bottom of the pan, only slightly overlapping them. Use the thickest and biggest potatoes on the bottom.
- Next, add half of the onions, half of the mushrooms, half of the basil, and half of the chard/spinach. Pour about half of the remaining sauce over this.
- Next, add another layer, starting with a layer of potatoes (use the smaller and any odd looking potatoes for this layer), followed by the remaining onions, mushrooms, basil, and chard/spinach.
- Now, finish the casserole with a final layer of potatoes, creating a nice-looking “roof” to your casserole. Pour the remaining sauce evenly over the top. ( The layers can get pretty high, but if using a regular 9×13 dish (not deep dish), just press down on the layers with your hands before placing this last layer of potatoes).
- Cover the dish with a glass lid (if it has one) or aluminum foil (make sure the foil doesn’t touch the food, and seal the edges). Bake for 35 minutes, or until the potatoes are tender when pierced with a knife and the edges are lightly browned. Let stand for 5 minutes before serving.