4 portobella mushrooms
2 tablespoons spicy mustard
3 tablespoons balsamic vinegar
½ cup olive oil
Dash of hot pepper sauce
Freshly ground black pepper

Mix together the mustard, balsamic vinegar, olive oil, hot pepper sauce and black pepper.
Brush mixture over both sides of portobella mushrooms. Grill or broil 4-5 minutes on each side.
Serve on a bun with fixings of your choice (tomato, lettuce, pickles, pesto, red onion, etc.)

Serves 4