Portobello and Spinach Sandwich

1. 1

   In a small bowl combine the first 4 ingredients.

2. 2

   Set aside.

3. 3

   Clean mushrooms with a damp cloth and lay them in a rimmed baking dish, smooth side down.

4. 4

   Spoon the vinegar mixture into the mushroom caps and let them sit 15-20 minutes.

5. 5

   Heat a large skillet on medium-high.

6. 6

   Spray skillet with non-stick spray and add onion.

7. 7

   Cook until onion is soft and light brown.

8. 8

   Remove onion from the skillet and set aside.

9. 9

   Spray skillet with spray again and add spinach.

10. 10

    Cover skillet and cook 3-4 minutes until spinach is wilted.

11. 11

    Remove it from the skillet and set aside.

12. 12

    Wipe out skillet and spray with oil spray.

13. 13

    Add mushrooms smooth side up and cook for 5-6 minutes.

14. 14

    Turn them over and cook for 2-3 minutes more.

15. 15

    Remove mushrooms from the skillet and top the smooth side with 1 piece of cheese each.

16. 16

    Assemble burgers by layering from the bottom up: bottom half of sandwich roll, 1/4 of spinach, a mushroom, 1/4 of the onion and the top roll piece.

* Per serving · 4 servings · Values may vary.