Prepare a medium-hot fire in a charcoal grill with a cover, or pre-heat a gas grill to medium-high. For best results, use a non-stick grill which helps to avoid adding oil.
On the stove, heat 2 tsp olive oil in a non stick skillet. When oil is hot, place celery and green onion in pan. Season with salt and pepper. Cook until soft, about 8-10 minutes. Set aside to cool. We are going to add these to our burger mixture later.
In the same nonstick skillet, heat 2 tsp olive oil in . When oil is hot, place sliced onion in pan. Season with good pinch of salt and pepper and cook. Saute onions until browned and caramelized, about 15-20 minutes, stirring occasionally.
While onions are caramelizing, prepare basting sauce and chipotle Sauce.
Combine low-fat yogurt and Chipotle Tabasco in a small bowl and mix well. Cover and refrigerate until ready to use.
Combine barbecue sauce and mango chutney in small bowl and mix well. Cover and refrigerate until ready to use.