The cardinal sin in carbonara is cream. It is also, if the historical record is to be believed, the way Bobby Flay made his.
Bruce Kalman — the Italian-American chef who built Union in Pasadena and now runs SoulBelly BBQ in Las Vegas — used guanciale, two cheeses (Pecorino plus Parmigiano), egg yolks, and the residual heat of the pasta to emulsify the sauce. No cream. No half-and-half. No dairy at all beyond the cheese. This is how a Roman makes it. This is also how a man who has thought about pasta carbonara for the last twenty years would make it.
Bobby finished second, in the language of the show — which is the polite way of saying he came in second of two.