Add the ketchup, bbq sauce, and mustards to the cooked beef. Set aside.
Slice Mushrooms and cook over a medium heat until soft.
Cold Toppings
Cut cherry tomatoes in half
Chop the pickles and red onion
Cut the avocado into bit sized chunks
Layer all ingredients on top of the prepared lettuce / thousand island mixture. Start with the cheese, then meat and mushrooms, followed by the rest of toppings.
Notes
Homemade Croutons are easy to make and a nice addition to this recipe
Adjust the amount of toppings based on your liking