Powdered/pre-shreddded cheese has some cornstarch or potato starch mixed in as anti-clumping agent. As you mentioned, when mixed into a liquid sauce, you get lumps from the starch. Great video once again, George. Love it
instead of the chicken stock, you can use the grease that comes from the bacon (ideally guanciale - cheek - or pancetta). Just cook the bacon first and then set aside the fat to go into the egg sauce. It helps to emulsify that better as well.