Make the ground beef mixture by heating 1 tablespoon of oil in a large skillet over medium-high heat. Add the onion and cook, stirring often, for 4-5 minutes.
Add the ground beef, breaking it up into crumbles with your spatula as it browns, and cook, stirring often, for 4-5 minutes.
Add the garlic and cook, stirring constantly, for 1 minute. Drain excess grease then add the taco seasoning. Toss to coat evenly and cook for 2 minutes.
Add the water and simmer for 10 minutes. Taste and add salt and pepper, if needed.
Make the crispy tostada shells by preheating the oven to 225 degrees and line a baking sheet with parchment paper.
Fill a small skillet with vegetable oil until it is 1/2 inch up the sides. Heat the oil over medium-high heat until hot, about 7-10 minutes. Test the oil by putting the tip of a corn tortilla in the oil, if it bubbles a lot, it’s ready. Side Note: Your tostada will be soggy if you add the tortilla to oil that is not hot enough.
When the oil is HOT, carefully place 1 corn tortilla in the hot oil then poke a few holes in the center with a fork to allow steam to exit.
Fry 1 tortilla at a time, holding metal potato masher in an upright position on top of tortilla to keep it submerged until crisp and lightly browned, 45 to 60 seconds; flip and cook for an additional 45-60 seconds, or until golden brown.
Drain both sides on paper towels then immediately sprinkle with a bit of sea salt and set aside while you repeat the process with the other tortillas.
To serve the tostadas, spoon on the refried beans followed by the ground beef mixture. Top with shredded lettuce, tomatoes, avocado slices, green onions, cotija cheese, and crema.
Serve immediately with salsa and hot sauce on the side. Enjoy.