Grilled Portabella and Brie Burgers

The following recipe, just in time for the grilling season, won first place in the Mushroom Council's Portabella Sandwich Contest.

• Ready In: 30 mins
• Serves: 4

Ingredients

• 1⁄4 cup  Italian salad dressing
• 4  large portabella mushroom caps
• 4  slices sweet onions, one slice for each burger slice thick
• 2  tablespoons  prepared pesto sauce
• 1  tablespoon mayonnaise
• 4  sandwich buns, split and lightly toasted
• 4  ounces fresh spinach leaves
• 2  tomatoes, sliced
• 4  ounces  ripe  brie cheese, rind removed, at room temperature

Directions

1. Prepare grill or preheat grill pan. Brush salad dressing on both sides of the portobello caps and onion slices. Grill portobellos and onions on both sides until mushrooms soften and onions are lightly browned; drain portobellos well on paper towels. Combine pesto and mayonnaise in a small bowl.
2. To assemble burgers: Spread pesto mayonnaise on bottom halves of rolls; top with spinach, tomato, grilled onions, and portobellos. Spread top halves of rolls with Brie and place on burgers.