Portobello Mushroom Burgers

I'm not sure why, but a few weeks ago I decided that I wanted to make burgers out of portobello mushrooms, so I did a Google search, bought some mushrooms, and came up with these burgers. They're easy, juicy, and super flavorful. Not to mention much healthier than a traditional beef patty.

\Burgers
6 portobello mushrooms, cleaned and stems cut off
1/4 cup balsamic vinegar
2 tbsp. olive oil
Dash salt
6 whole wheat hamburger buns

Toppings 
1 red bell pepper, sliced into rings
1 medium red onion, sliced into rings
2 tbsp. olive oil
Dash salt
2 tomatoes, sliced
Hummus
12 sandwich pickle slices

To make the burgers: combine 2 tablespoons of vinegar and 1 tablespoon of olive oil into each of two large freezer bags. Add 3 mushrooms to each bag. Seal, and shake the bags gently until the mushrooms are covered. Let sit flat for at least 15 minutes.

In a large pan, saute the bell pepper and onion in the oil and salt over medium-high until well done. 

In a separate pan, cook the mushrooms with their extra marinade 5-8 minutes on each side, until the mushroom and dark, tender, and looks shrunken.

Toast the buns if desired. Spread hummus on both sides. Add a mushroom to each bun. Divide the pepper, onion, tomatoes, and pickles evenly among the buns.