Portobello Sandwiches

Name: Portobello Sandwiches
Ingredients: 2 cloves garlic, minced; 6 tablespoons olive oil; 0.5 teaspoon dried thyme; 2 tablespoons balsamic vinegar; salt and pepper to taste; 4 large portobello mushroom caps; 4 hamburger buns; 1 tablespoon capers; 0.25 cup mayonnaise; 1 tablespoon capers, drained; 1 large tomato, sliced; 4 leaves lettuce