Preheat the oven to 180 degrees celsius (fan-forced). Lightly grease a large round baking dish (approx 30cm diameter) and set aside.
Place the onion into the Thermomix bowl. Chop on Speed 6, 6 seconds. Scrape down the sides of the bowl.
Add the olive oil and minced garlic and saute for 3 minutes, 100 degrees, Speed 2.
Add the beef mince and the taco seasoning. Break up the mince and cook for 10 minutes, 100 degrees, Speed Soft, Reverse.
Add the tomato paste, diced tomates, frozen corn and beans and cook for 10 minutes, 100 degrees, Speed Soft, Reverse.
Place one tortilla onto the base of the baking dish. Top with 1/5 beef mince and sprinkle over some cheese. Repeat until you've used up all the beef mince.
Finish with a layer of tortilla and grated cheese.
Bake in the oven for 35 minutes or until golden and cooked through (see notes). Serve with sour cream and avocado slices.