1. Make the cilantro-avocado cream sauce. In a blender combine the cilantro, avocado, sour cream, lime juice, and a pinch of salt. Blend until smooth. Set aside.
2. Make the beef filling. Heat the oil in a large skillet over medium heat. When it begins to swirl, add the onions, salt, a few grinds of pepper, the cumin, and thyme. Cook, stirring, until the onions are tender, about 5 minutes. Add the garlic and cook until fragrant, about 5 minutes. Add the beef and break up with a spoon or spatula as it browns. When the meat is cooked through, taste and, if needed, season with a pinch of salt.
3. Fill the chimichangas. Warm the tortillas in a microwave for just a few seconds or in a 100degreesF oven for a few minutes. Divide the refried beans into 4 equal portions. Using a rubber spatula or the back of a spoon, spread the beans in the center of each tortilla, making a rectangle with the rough dimensions of 6 inches 3 inches.. Using this as a guide add the beef directly over the beans. On a 10-inch tortilla, this leaves 2 inches of tortilla on the rectangle's short side of the filling, and 31/2 inches of tortilla on the long sides.
4. Roll the chimichangas. With the length of the rectangle of fillings horizontal to you, use both hands to fold each end with the 2-inch border in and over the mound of beef. Then fold the 31/2-inch flap closest to you over the beef, tuck it in gently, but tightly, and roll the burrito away from you. Set aside. Rest with the seam side down and continue with the rest.
5. Fry the chimichangas. Fill a large straight-sided pan with an inch of oil and bring it to 360 degrees F. (The temperature will fall when the burritos are added.) When the oil is hot, add 2 burritos at a time, seam side down, keeping the temperature at 350 degrees F. Cook until golden on the bottom, then roll and cook all sides, about 8 to 10 minutes total. Transfer each to a paper towel-lined plate. Repeat with the second batch.
6. Top the chimichangas. Turn on the broiler or preheat your oven to 500 degrees F. Place each chimichanga on a baking sheet, seam side down. Mix the Cheddar and Jack cheeses in a bowl. Top each chimichanga evenly with an equal amount of cheese. Cook until the cheese melts, 2 to 3 minutes. Transfer each to a serving plate and top evenly with lettuce, avocado cream sauce, tomatoes, jalapeno slices, and radish slices.
Use this technique to make a breakfast or brunch chimichanga filled with black beans, scrambled eggs, cheese, and cooked sausage. Make smaller versions of this for kids using 6-inch soft taco shells.
(c) 2013 by Sunny Anderson. Photographs copyright (c)2013 by John Lee. Published by Clarkson Potter, a division of Random House LLC.