The ultimate vegan comfort food sandwich! These hearty open-faced sandwiches are made with savory turkey-style seitan slices and rich gravy piled onto slices of toasted crusty bread.
If using homemade seitan, slice it as thin as possible, preferably using a mandoline slicer. If using store-bought, slice it thin as best as you can using a mandoline or sharp knife (depending on the size and shape of your seitan pieces).
Place 1 tablespoon of vegan butter in a medium skillet and melt it over medium heat.
Give the butter a minute to heat up, and then add the seitan slices. Avoid overcrowding the skillet, and cook the slices in batches if needed.
Cook the seitan slices for about 5 minutes on each side, until lightly browned, and then remove them from the skillet and transfer them to a plate.
Melt the remaining 2 tablespoons of butter in the skillet.
Add the onion and cook for about 5 minutes, until soft and translucent.
Add the garlic and flour, and stir well to coat the onions with flour. Cook for about 1 minute more, until the garlic becomes very fragrant.
Whisk in the water, milk, nutritional yeast flakes, soy sauce, vinegar, thyme, and rubbed sage.
Raise the heat and bring the mixture to a simmer. Lower the heat and allow it to simmer, uncovered, for about 10 minutes, until it thickens up a bit.
Return the seitan slices to the skillet and stir them into the gravy. Cook for about 1 minute more, just to heat up the seitan and give it a chance to absorb some gravy.
Remove the skillet from heat and season the gravy with salt and pepper to taste.
Arrange the bread slices on plates in pairs, and top with the turkey and gravy. Sprinkle with parsley and/or chives, and serve.