In a large skillet, cook the ground beef until it is browned. Drain off any excess fat and add the taco seasoning mix.
Add the diced tomatoes, green chili, and refried beans to the skillet. Mix well and cook over medium heat for about 10 minutes, stirring occasionally.
In a separate bowl, mash the avocados with a fork until they are smooth. Add in the evaporated milk and mix until combined.
Add the mashed avocado mixture to the skillet with the ground beef and other ingredients. Mix until everything is well combined and cook for an additional 5-10 minutes, stirring occasionally.
Once everything is cooked through, add in the Velveeta cheese and diced onion. Stir until the cheese is melted and everything is well combined. Serve it.