Instructions

Transfer ground meat to medium bowl. Stir in salt, pepper, Worcestershire sauce, ricotta cheese, and mustard until blended, and divide meat into 4 portions. Lightly toss one portion from hand to hand to form a ball, then lightly flatten ball with fingertips into 1-inch-thick patty. Repeat with remaining portions.
TO COOK INDOORS: Heat a large, heavy skillet (preferably cast-iron or stainless steel with an aluminum core) over medium heat until very hot, 4 to 5 minutes. Swirl oil in pan to coat bottom, then add burgers. Cook over medium heat without moving burgers until bottom side of each is dark brown and crusted, 3 to 4 minutes. Turn burgers over; continue to cook until bottom side is light brown but not yet crusted, 3 to 4 minutes longer. Reduce heat to low, position cover slightly ajar on pan to allow steam to escape, and continue to cook 8 to 10 minutes longer, flipping burgers if necessary to promote deep browning, until center is completely cooked, or an instant-read thermometer inserted from the side of the burger into the center registers 160 degrees. Remove from pan and serve immediately.TO GRILL: Alternatively, grill burgers over medium-low fire (you can hold your hand about 5 inches above grill surface for 5 seconds) until dark spotty brown on bottom side, 7 to 9 minutes. Turn burgers over; continue grilling 7 to 9 minutes longer or until bottom side is dark spotty brown and center is completely cooked or instant-read thermometer registers 160 degrees. Remove from grill and serve immediately.