In a suitably sized bowl combine all of your ingredients for the sour cream, test for seasoning, then cover and pop in the fridge until needed.
Brush all sides of your onions, peppers and jalapeños with olive oil and season with a pinch of salt and pepper. Place evenly on 4 separate skewers (see video for guidance).
Place on the BBQ until charred, flipping once and spraying both sides with the marinade. Take off and place to one side.
BBQ the burgers until just cooked throughout, flipping once. Move to one side of the BBQ away from direct heat.
Grab a pan and place it on the BBQ, add a slice of cheese to the pan and leave until it begins to melt. Add one of the burgers and place on top of the cheese until it gets crispy. Repeat for all burgers (or do all at once in a suitably sized pan).
Place your buns on the BBQ to toast (optional).
Stack by spreading 1 tbsp guac on your base bun, topped with lettuce, followed by your burger, followed by your peppers & jalapeños (sliced if desired) and finish by spreading your sour cream sauce on the other half of your bun.