Heat a pan/skillet over medium heat, add in ground beef. While you are browning and breaking it up add in the diced onion. Once beef is browned add in the other ingredients stir together, bring to a simmer and allow to go for about 15 minutes so it can thicken up.
While making the chili, cook tater tots as per the directions on the package.
Once both are done line a backing sheet or cast iron skillet with tater tots, spoon the chili over the tots, and lastly the shredded cheese. Bake at 375˚ for 6 to 10 minutes, just long enough for the cheese to get nice and melty.
While the totchos are in the oven, in a small bowl mash avocados, lime juice, and salt together until it is nice and smooth.
Place diced green onion and sour cream on top of cooked totchos and serve with the avocado mash.