True culinary blue, known historically in French kitchens as bleu, is not simply an undercooked rare steak. It requires rapid searing technique that applies extreme surface heat for mere seconds to pasteurize the exterior while leaving interior structural proteins uncontracted and cool.
| Doneness Level | Target Internal Temperature | Visual & Textural Profile | Core Cooking Technique |
|---|---|---|---|
| Blue Rare (Bleu) | 100°F, 115°F | Deep red to purple core; soft, cool or lukewarm interior; thin crust. | Flash-sear on blistering heat (60, 90 seconds per side); immediate removal. |
| Pittsburgh Rare | 110°F, 120°F | Heavily charred, blackened crust; bright red, cold-to-cool center. | Direct open flame or screaming-hot cast iron with butter/tallow to induce char. |
| Traditional Rare | 120°F, 125°F | Bright red throughout; warm center; soft yielding texture. | High-heat sear followed by short indirect resting period. |
| Medium Rare | 130°F, 135°F | Warm pink center; fully rendered fats; balanced firmness. | Standard commercial grill or broiler cycle with controlled carryover rest. |
Regional variations complicate diner expectations. Steelworkers in Pennsylvania originated Pittsburgh rare, often termed "black and blue", by throwing cold meat directly against industrial machinery pipes or superheated foundry iron. That method demands a heavily carbonized, blackened exterior contrasting with a cold interior. A standard blue rare steak, by contrast, avoids heavy charring, aiming only to kill surface bacteria while locking in natural juices.
