This is what I used for one sandwich. Double, triple, etc. as needed
2 pieces of bread
1/2 of an avocado
1/2 of a lime
2 slices of your favorite cheese (I used white cheddar)
2 large tomato slices
1 small onion
1 large handful of fresh spinach
1 medium portobello mushroom
Salt and pepper
First make the simple guacamole. Scoop out 1/2 of an avocado and add it to a bowl. Sprinkle salt and pepper over it and the jucie from 1/2 of a lime. Mash together with a fork or potato masher until just slightly chunky. Set aside.
Slice the onion into thin slices. Add about 1 tablespoon olive oil to a pan over medium-high heat. Once hot, add the onion and cook for several minutes, or until the onion begins to brown. I made sure that the pan was nice and hot so that the onion cooked and browned quickly. Once slightly browned, add a splash of white wine to the pan and let it cook off. Once the wine has cooked away, place the onions in a small bowl and set aside.
Add a large handful of spinach to the same pan as the onion, over medium high heat. Cook, stirring constantly, until the spinach begins to wilt. Add another splash of white wine and continue to cook and stir until the wine has again cooked away. Remove the spinach from the pan as well and set aside.
Wipe the mushroom clean with a paper towel. Remove the stem and brown scaly insides. Slice the mushroom into long strips. Add another tablespoon of olive oil to the same pan over medium-high heat. Once hot, add the mushroom strips and stir around to coat the mushrooms in oil. Let cook for several minutes, until the mushroom begins to get soft. Add a large splash of balsamic vinegar to the pan, stir, and let cook several more minutes, until the vinegar has cooked away. Remove the mushrooms from the pan and set aside.
To make the sandwich, butter one side of each piece of bread. Make the grilled cheese however you usually make one, layering the cheese and veggie layers.
How I did it: place one piece of bread in a pan over medium heat. Add the guacamole, tomato slices, one slice of cheese, onions, spinach, mushrooms and then another slice of cheese. Let cook until the bread is crsipy and browned. Add the other piece of bread on top, buttered side up. Using a large spatula, quickly but carefully flip the sandwich. Let cook until the other slice of bread is crispy. Smash down a bit to combine everything together, slice and eat.