For the pickled carrots:
½ cup rice vinegar
2 tablespoons sugar
½ teaspoon salt
For the marinated mushrooms:
Juice of ½ lime (about 2 tablespoons)
2 tablespoons light brown sugar
1 tablespoon rice vinegar
2 teaspoons soy sauce
2 cloves of garlic, minced
¼ teaspoon sriracha sauce
3 portobello mushroom caps (about 6 ounces total), cut into 1” strips
For the sandwich:
1 large baguette
2-3 tablespoons mayonnaise
½ medium-sized seedless cucumber
½ jalapeno pepper, thinly sliced
¼ cup cilantro leaves
1 teaspoon soy sauce
Make the pickled carrots:
In a small saucepan, bring the vinegar, sugar, and salt to a boil. Remove the mixture from the heat and let it cool for 5 minutes.
In the meantime, peel and coarsely shred or finely julienne the carrots, then transfer the shredded carrots to a non-reactive bowl or container. Pour the vinegar mixture over the carrots. Refrigerate overnight. (If you’re in a rush, you can leave it at room temperature for an hour, but overnight is best.)
Prepare the mushrooms:
Mix all the ingredients for the marinade in a quart-sized plastic bag. Add the mushroom strips and marinate overnight in the refrigerator or for 1 hour at room temperature.
Assemble the sandwich:
Heat oven to 400° F.
Put the marinated mushroom strips and the marinade in a baking dish and bake until the mushrooms are soft, about 12 minutes. Let them cool for at least 5 minutes.
Cut the baguette open by slicing it in half but not going all the way through. Spread the mayonnaise on one side of the baguette. Place the baguette on a baking sheet and heat it until it is crisp and lightly browned, about 6-8 minutes. Let it cool for a few minutes before assembling the sandwich.
In the meantime, cut the cucumber lengthwise into ¼” thick slices and squeeze the liquid out of the pickled carrots.
Assemble the sandwich by arranging the cucumber slices in a single layer on the baguette, then topping them with the mushrooms, pickled carrots, and cilantro. Sprinkle the soy sauce on top and close the sandwich.
Cut into 3 or 4 sections and serve.