Step 1

Preheat oven to 300 °F (150 °C). Line a large baking sheet with parchment paper.

Step 2

Prepare mushrooms by removing stems and cleaning with a damp cloth or paper towel. Slice mushrooms.

Step 3

Toss the sliced mushrooms with the olive oil and tamari until well coated and place on baking sheet so that the mushrooms are not touching. Bake for 30-40 minutes, tossing halfway through, until the mushrooms are shriveled and crispy.

Step 4

Assemble the sandwiches on the bread with a slather on mayo, the arugula, sliced tomatoes, and the crispy shiitake mushrooms.