Step 1

Heat oven to 400°F.

Step 2

In 5-quart Dutch oven, cook beef, onion and garlic over medium-high heat 7 to 9 minutes, stirring occasionally, until beef is no longer pink. Add mushrooms; cook, stirring occasionally, 4 to 6 minutes longer or until mushrooms are tender and brown. Stir in broth, tomatoes, grill seasoning, salt and pepper. Heat to boiling; reduce heat. Cook uncovered 10 minutes, stirring occasionally.

Step 3

Meanwhile, split burger buns in half, and place cut sides up on ungreased cookie sheet. In small bowl, mix mayonnaise and garlic powder. Spread 1/2 teaspoon mayonnaise mixture on each bun. Toast buns in oven 5 to 7 minutes or until light golden brown and crisp.

Step 4

Serve soup topped with toasted bun, bacon and Swiss cheese.