Place mince, mushrooms, tarragon, mustard and egg in the bowl of a food processor and blend until combined. Remove from the bowl, season with salt and pepper and form into 4 patties.
Pre-heat an oiled char-grill pan or BBQ over medium high heat. Cook burger patty for 3-4 minutes, turn and top with sliced cheese. Cook for a further 3-4 minutes or until cheese is melted and patty is cooked to your liking. Set aside to keep warm.
Cook bacon for 2-3 minutes each side or until golden and crisp, set aside to keep warm
Add mushrooms to pan or BBQ, turning until mushrooms are grilled on both sides and warmed through. Remove from the heat
Spread base of burger rolls with mayonnaise, top with iceberg lettuce, Portabella Mushroom, tomato, beef patty, bacon and drizzle with tomato chutney to serve.