Preheat your grill to medium-high heat.

Clean the Portobello mushrooms by gently wiping them with a damp cloth or paper towel to remove any dirt.

In a small bowl, whisk together the balsamic vinegar, olive oil, minced garlic, salt, and pepper to make the marinade.

Brush both sides of the Portobello mushrooms with the marinade, ensuring they are well coated.

Sprinkle the mushrooms with fresh herbs for added flavor.

Place the mushrooms on the preheated grill, gill-side down.

Grill the mushrooms for 4-5 minutes per side, or until they are tender and have grill marks.

Remove the mushrooms from the grill and cover with aluminum foil.

Serve the grilled Portobello mushrooms as a main dish or as a burger substitute.