Sauté the beef, onions and garlic till the meat is browned and cooked through, drain off the fat. Transfer the meat mixture to a mixing bowl and let it cool. Once the meat is cool enough to handle crumble it into tiny pieces with your fingers. Mix in the salsa, refried beans, and the optional chilies in a bowl till all is thoroughly combined. Return everything to the skillet and heat till bubbly and warm throughout, lower heat and slowly simmer for 5 minutes.
Spread the chips in glass casserole dish, evenly top with the beef/bean mixture. Evenly spread the cheese over all and microwave on high till the cheese is melted, about 2 minutes in a 1000W oven.
Top the nachos with tomatoes, green onions, olives, peppers. Scoop the sour cream and guacamole into the corners.