Step 1: Brown the Beef - Start by heating a large skillet over medium heat, then add the ground beef. Break it apart as it cooks, using a wooden spoon or spatula, and keep going until there is no pink left. I like to take a minute here and really crumble the beef well, because smaller pieces spread more evenly through the casserole and give you that good taco filling in every bite.
Step 2: Season the Beef - Once the beef is browned, stir in the salt, pepper, and taco seasoning. Let it cook for another minute or two so the seasoning can warm up and cling to the meat. If there is extra grease in the pan, drain it off before layering. You want the casserole rich and cheesy, not oily, and this little step makes the finished dish taste cleaner.
Step 3: Mix the Creamy Chipotle Rice - In a large bowl, stir together the nacho cheese sauce or queso, sour cream, chipotle sauce, uncooked long grain white rice, beef broth, and drained Rotel. This mixture may look a little loose at first, but that is exactly what you want. The rice needs that liquid to cook slowly and become tender. Give it a good stir so the queso, sour cream, and chipotle sauce are evenly mixed.
Step 4: Grease the Slow Cooker - Lightly grease the inside of your slow cooker before adding anything. I know it sounds like a small thing, but future you will be thankful when cleanup is easier. A little cooking spray or a light rub of oil around the bottom and sides helps keep the cheesy edges from sticking too much.
Step 5: Start the First Beef Layer - Spread a thin layer of the seasoned beef mixture across the bottom of the slow cooker. This gives the tortillas something flavorful to sit on and helps keep the bottom layer from turning plain. You do not need a thick layer here. Just enough to cover the bottom is perfect.
Step 6: Add the Tortilla Layer - Lay flour tortillas over the beef, tearing them as needed so they fit the shape of your slow cooker. This is not a beauty contest, and nobody is going to see those torn pieces once everything cooks together. Think of it like making a cozy taco lasagna. The tortillas soften as they cook and give the casserole that burrito inspired texture.
Step 7: Add Beef, Rice, Crunch, and Cheese - Spoon more seasoned beef over the tortillas, then add some of the creamy chipotle rice mixture. Sprinkle on some crushed tortilla strips and a handful of Mexican blend cheese. This is where the casserole really starts to build flavor. You get meat, creamy rice, salty crunch, and melted cheese all tucked into each layer.
Step 8: Repeat the Layers - Keep repeating the layers until all the ingredients are used, finishing with cheese on top. Try to spread the rice mixture evenly as you go so the rice cooks at the same pace throughout the slow cooker. I like to press the layers down gently with the back of a spoon, not smashing them, just helping everything settle in together.
Step 9: Slow Cook Until Tender - Cover the slow cooker and cook on low for 4 to 5 hours or on high for 2 to 3 hours. The casserole is ready when the rice is tender, the filling is hot, and the cheese is melted and bubbly. Slow cookers can run a little differently, so start checking near the lower end of the time range. If the rice still has a bite to it, give it a bit more time.
Step 10: Add the Cheddar Grilled Cheese Finish - During the last 15 minutes of cooking, sprinkle the shredded cheddar cheese over the top. Cover it again and let that cheddar melt into a gooey golden layer. This is the part that gives the casserole its grilled cheese burrito personality. It is rich, melty, and the kind of top layer someone will definitely try to sneak a spoonful from.
Step 11: Finish and Serve - Right before serving, drizzle extra chipotle sauce over the top and sprinkle with extra tortilla strips. The sauce adds that smoky fast food style finish, and the tortilla strips keep the top crunchy. Let the casserole sit for 5 to 10 minutes before scooping so it thickens up a little and serves more neatly.