A good vegan sandwich needs some careful thought and construction. It has to have a good balance of textures and flavors, but it should also be satisfying without relying on meat or cheese. Portobello mushrooms are a popular ingredient choice (for good reason), and this one is no exception. Throw some sourdough bread in the toaster and let's get cooking!
While searing the portobello mushroom whole seems like the easiest way to cook it, I like to slice the mushroom first so that there are lots of cut sides that can brown and get flavorful. Drizzling a little balsamic vinegar into the pan at the end gives a brighter flavor to the earthy mushrooms.
A sandwich like this needs an assertive spread like a garlicky aioli to hold it all together. You only need a small amount of garlic, though, so I like to rub a cut clove onto just-toasted bread, similar to what the Spanish do with tomatoes when making pan con tomate. After the garlic comes a thin layer of mayonnaise; the type you use is up to you. Vegan mayo, homemade or otherwise, keeps this sandwich strictly animal product-free.
The sandwich is finished with tender baby spinach leaves and sweet roasted red peppers. It's colorful, fresh, and satisfying, but won't weigh you down into a food coma post-lunch.
Vegan Sourdough Portobello Mushroom Sandwich
Makes 1 sandwich
medium portobello mushroom (at least 3 ounces), scrubbed clean and stem removed
Freshly ground black pepper
sourdough sandwich bread
garlic, halved lengthwise
regular or vegan mayonnaise
packed baby spinach leaves
roasted red peppers
If you'd like, scrape the black gills from the underside of the mushroom and discard (they can be bitter). Cut the mushroom into 1/2-inch-thick slices.
Heat the oil in a medium frying pan over medium-high heat until shimmering. Add the mushroom and season with salt and pepper. Cook, moving rarely, until golden-brown all over, 5 to 6 minutes. Drizzle the vinegar over the mushrooms and stir to combine. Cook until the vinegar is completely absorbed into the mushrooms, about 1 minute. Remove the pan from the heat.
Toast the bread. Rub the cut side of the garlic on one side of each slice of bread. Spread a tablespoon of mayonnaise on each slice of bread. Place the spinach on one slice of bread, top with the mushrooms, and top the mushrooms with the red peppers. Place the other slice of bread mayonnaise-side down on top of the peppers to close the sandwich. Press down gently on the sandwich to compress and slice in half with a serrated knife before serving.
Make ahead: If the mushrooms are made ahead, this sandwich can be put together at the last minute with just the aid of the toaster in the office. Pack the spinach and peppers separately. Toast the bread and proceed with assembling the sandwich.