Stuffed Cheesy Portobello Burgers

Ingredients:

2 tablespoons butter

2 Vidalia onions, thinly sliced
4 large portobello mushrooms, stems removed and caps cleaned
Olive oil, for brushing
Kosher salt and freshly cracked black pepper
1 tablespoon brown sugar
1 teaspoon balsamic vinegar
1/2 cup shredded sharp white Cheddar
1/2 cup shredded Swiss
4 kaiser rolls, split, buttered and toasted
4 slices tomato
1 cup baby arugula
Roasted Garlic Aioli, recipe follows

Roasted Garlic Aioli:

1 head garlic
1 tablespoon olive oil
Kosher salt and freshly cracked black pepper
1/2 cup mayonnaise
1 teaspoon lemon juice

Directions:

In a large skillet, melt the butter over medium heat. Add the onions and cook just until translucent, about 5 minutes. Add the brown sugar and balsamic vinegar, cover and continue cooking, stirring occasionally, until the onions are caramelized, 20 to 25 minutes.

Meanwhile, heat a grill, grill pan or cast-iron skillet over medium-high heat. Brush the tops of the portobello mushrooms with olive oil and season liberally with salt and pepper. Cook the mushrooms, stem side down, 5 to 7 minutes. Flip and continue cooking another 5 minutes. Remove to a work surface.

Fold the shredded cheeses into the caramelized onions just before building the burger. Carefully spoon the caramelized onions and melted cheese into the mushroom caps.

Build the burger by placing each stuffed mushroom on the bun bottoms. Top with the tomatoes and arugula. Smear the top buns with the Roasted Garlic Aioli and place on top of the other ingredients. Serve immediately.

Recipe shared from: http://www.cookingchanneltv.com/recipes/kelsey-nixon/stuffed-cheesy-portobello-burgers-recipe/index.html