01 - Brown ground beef in a skillet, breaking it into small pieces, until it reaches 160°F. Drain excess fat, add taco seasoning and the half cup water, and simmer until the mixture is thick rather than watery.
02 - Warm cooked rice and nacho cheese sauce as appropriate for their storage state. Warm tortillas briefly until pliable. Divide beef, rice, cheddar, nacho sauce, sour cream and crushed chips among four tortillas, leaving clear borders. Serve excess filling alongside.
03 - Fold in both sides and roll tightly. Melt a little of the measured butter in a nonstick skillet over medium-low heat and toast each wrap seam-side down until sealed.
04 - Lift a wrap, scatter a quarter cup mozzarella in a narrow patch of the pan, and place the wrap onto it. Let cheese melt and develop golden edges before loosening carefully with a thin spatula. Repeat with remaining wraps and remaining butter as needed.
05 - Use already-hot fillings; a short toast does not reliably reheat a cold center. Let the wraps rest briefly before slicing and serve while the exterior is crisp.